Turbofan Engine Malfunction Recognition and Response Final Report

Home , Accessory drive, Compressor stall, Flameout, Foreign object damage

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Foreword

This document summarizes the work done to develop generic text and video training material on the recognition and appropriate response to turbofan engine malfunctions, and to develop a simulator upgrade package improving the realism of engine malfunction simulation. This work was undertaken as a follow-on to the AIA/AECMA report on Propulsion System Malfunction Plus Inappropriate Crew Response (PSM+ICR), published in 1998, and implements some of the recommendations made in the PSM+ICR report. The material developed is closely based upon the PSM+ICR recommendations.

The work was sponsored and co-chaired by the ATA and FAA. The organizations involved in preparation and review of the material included regulatory authorities, accident investigation authorities, pilot associations, airline associations, airline operators, training companies and airplane and engine manufacturers.

The FAA is publishing the text and video material, and will make the simulator upgrade package available to interested parties. Reproduction and adaptation of the text and video material to meet the needs of individual operators is anticipated and encouraged. Copies may be obtained by contacting:

FAA Engine & Propeller Directorate ANE-110 12 New England Executive Park Burlington, MA 01803

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Contributing Organizations and Individuals

Note: in order to expedite progress and maximize the participation of US airlines, it was decided to hold all meetings in North America. European regulators, manufacturers and operators were both invited to attend and informed of the progress of the work.

Air Canada Capt. E Jokinen ATA Jim Mckie AirTran Capt. Robert Stienke Boeing Commercial Aircraft Van Winters CAE/ Flight Safety Boeing Capt. Kip Caudrey Continental Airlines Jackson Seltzer Delta Airlines Tim Hester Capt. John Sciera FAA Ann Azevedo Ed Cook Karen Curtis GEAE Sarah Knife Paul Mingler Jack Stopkotte JAA Laurent Gruz Northwest Tony Hunt David James Ohio State U Jerry Chubb Purdue University Mark Thom Pratt & Whitney Dick Parker Bob Valli Al Weaver (ret’d) TSB Canada Bruce McKinnon Nick Stoss United Airlines Rick Bobbitt Pete Delo Steve Ferro Erwin Washington US Airways Ron Thomas Volpe Center Judith Burki-Cohen

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Introduction

On 13 December 1994 a Jetstream 31 turboprop crashed at Raleigh Durham, resulting in fatal injuries to 15 passengers and two crew. It was determined by the NTSB that the pilot had mistakenly assumed that an engine had failed and subsequently failed to respond appropriately. The AIA, at the request of the FAA, subsequently undertook a project to identify the issues related to the accident and identify corrective actions. The results of the AIA/AECMA project were published in 1998 (Reference 1). Key findings of the AIA/AECMA Project Group included:

• Although the vast majority of propulsion system malfunctions are recognized and handled appropriately, there is a shortfall in some pilot’s abilities to recognize and handle propulsion system malfunctions. The shortfall from initial expectation is due to improved modern engine reliability, changing propulsion system failure characteristics (symptoms), changes in flight crews’ experience levels, and related shortcomings in flight crew training practices and training equipment.

• Industry has not provided adequate pilot training processes or material to ensure pilots are provided with training for powerplant malfunction recognition. This shortfall needs urgent action to develop suitable text and video training material which can be used during training and checking of all pilots for both turboprop and turbofan powered airplanes..

• The training requirements related to “Recognition and correction of in-flight malfunctions” are found in Appendix C of 14 CFR Part 63 for Flight Engineers. The disposition of the flight engineers recognition training requirements to pilots of airplanes where no “Flight Engineer” position exists is not apparent. However, the expectation does exist that the pilots will perform the duties of the flight engineer.

• The review of simulator capabilities shows that the technology exists to better produce realistic propulsion system malfunction scenarios. However, at the moment, realistic scenarios are often not properly defined nor based on airframe or powerplant manufacturers’ data. Rather, the scenarios are often based on the customers’ perceptions of the failure scenario. There is generally no airframe or powerplant manufacturers’ input into realistic engine failure/malfunction scenarios as represented in simulators. Furthermore, the engine failures currently addressed in most training do not cover loud noises and the onset of heavy vibration. Complete and rapid loss of thrust is currently being trained and is probably the most critical from an airplane handling perspective; however, this failure is not necessarily representative of the malfunctions most likely to be encountered in service. There is also evidence that this lack of realism in current simulations of turbofan propulsion system malfunctions can lead to negative training, increasing the likelihood of inappropriate crew response. Review of current simulators indicates that the tactile and auditory

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representation of airplane response to engine compressor stall/surge is very misleading.

• A substantial number of the turbofan accidents reviewed are related to propulsion system malfunctions resulting in high-speed aborts, including above V1 and Vr. Accordingly, current pilot training may be deficient in addressing the symptoms of the malfunctions, particularly loud noises and the importance of V1 and Vr speeds. There was only one RTO-related accident identified on turboprop airplane in the database.

The AIA/AECMA report included a recommendation that :

The aviation industry should undertake the development of basic generic text and video training material on turboprop and turbofan propulsion system malfunctions, recognition, procedures and airplane effects.

The FAA and ATA accordingly sponsored an industry/regulatory team, in September 1999, to develop such training material for turbofans (see Appendix 1). This report documents the activity of the team and summarizes the training material developed.

The team was divided into two sub-groups, one addressing the development of text and video material, co-chaired by engine manufacturer representatives, and the other addressing simulator realism, chaired by UAL and Boeing.

It was recognized that training material also needed to be developed for turboprops, but given the scarcity of resources available in the turboprop community, this activity was deferred until the turbofan material was under way. It was hoped that the turboprop activity would be able to leverage some of the turbofan work.

The training material provided is intentionally confined to description of engine operation and propulsion system malfunction, and to broad outlines of intended pilot response. Specific procedures may vary between aircraft models and also between operators; the training material was intended to avoid conflict with published procedures.

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Definitions and Acronyms

AECMA The European Association of Aerospace Industries AIA Aerospace Industries Association ATA Air Transport Association CVR Cockpit Voice Recorder FAA Federal Aviation Administration FADEC Full Authority Digital Electronic Control LOFT Line Oriented Flight Training NTSB National Transportation Safety Board PSM + ICR Propulsion System Malfunction + Inappropriate Crew Response (limited to those malfunctions which did not inherently render the aircraft not airworthy) RTO Rejected takeoff V1 Takeoff decision speed Vr Takeoff rotation sped

Inappropriate crew response: A crew response to a malfunction which was other than the response trained or defined in the AFM, and which led to an accident or serious incident.

Selection of Malfunctions to be Trained

Before either the text/video group or the simulator group could create training material, it was essential to agree upon the propulsion system malfunctions that should be addressed. The accident record shows that almost any malfunction can lead to inappropriate crew response and a subsequent accident, but that some are more likely to do so than others. It was decided that the malfunctions should be discussed in terms of the symptoms presented to the pilot rather than in terms of the detailed hardware failure, since similar symptoms were likely to prompt similar responses, and since detailed discussion of hardware would make preparation of generic training material very difficult.

A poll of current simulators conducted by FAA-Flight Standards, in the work of the AIA PSM+ICR group, showed that a large variety of engine malfunctions are available in the simulators. There is no current guidance on which are the most valuable to the pilot and which should be trained. Only a few of these malfunctions are actually used by each operator, and their selection is at the discretion of the instructor. One of the most frequently used malfunctions – an engine flameout at V1 – is almost never encountered in service. Current practice, therefore, was not felt to be a good basis for what should be trained.

It was recognized that each pilot would only have very limited time available in the simulator and that only a select few propulsion system malfunctions would be trained in that environment. A training video offered the opportunity to cover a wider variety of

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engine malfunctions, and the text material could cover as many malfunctions as the team considered of interest. The constraining factor, therefore, was the simulator time available to train engine malfunctions, and the requirement that the training footprint in the simulator not be greatly increased.

Selection criteria

The following considerations were felt important in selection of malfunctions to be trained in the simulator:

• Observed likelihood of crew error (based on the PSM+ICR database) • Severity of results of crew error (whether fatalities or significant aircraft damage resulted) • Frequency of propulsion system malfunction • Opportunity for improved training to reduce the likelihood of error

Malfunction Approximate relative frequency Bird ingestion/FOD (mostly very minor) 100 Flameout/rollback (generally from low power settings) 50 Fire warning (mostly hot air leaks) 33 Stall (broad spectrum of severity) 38 Severe engine damage 32 Seizure .3 Reverser inadvertent deploy (in flight) .01 Engine separation .01

Selection process

A matrix of propulsion system malfunctions was developed, showing the symptoms, historical inappropriate crew response, desired crew response and helpful training activity, by flight phase. This matrix had 49 separate combinations of malfunctions and flight phases. The malfunctions addressed were engine surge, engine power loss, fire warning and uncommanded thrust change/non-response to throttle movement. These were selected because they had caused multiple accidents due to inappropriate crew response.

The matrix was then summarized by eliminating those conditions (malfunctions at a given flight phase) which had not resulted in an accident or serious incident as a result of inappropriate crew response (see Table 1). The remaining conditions were prioritized according to the number of accidents/ incidents known to have involved those conditions. Seven conditions caused 54 of the 79 events in the AIA database (presented in Table 2). These were considered to be of the highest priority for training in the simulator, although in some cases the training would be so similar that duplication of a malfunction for all of the flight phases was not considered essential.

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The remaining 17 conditions accounted for a smaller proportion of the events, and it was agreed that in most of the cases, emphasis on maintaining control of the aircraft and verifying the identity of the engine with the problem would address these events, without the need for simulation.

The malfunctions addressed in the video included all those which had resulted in multiple accidents or incidents, according to the AIA database. There was a specific concern relating to engine vibration after an inflight shutdown, which had led one flight crew to question the structural integrity of the airplane; although this did not lead to any crew error or to an accident/incident, it was felt to be so unusual and alarming that it should be addressed in the video.

Since the text material did not have the same constraints as the simulator and video material, a wider variety of engine malfunctions were addressed. These included many malfunctions which have not resulted in accidents, but which occur with reasonable frequency in service on a wide variety of engines.

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Table 1

GROUP 1

PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT PHASE Immediate Failure Mode Response SURGE TAKEOFF > V1 LOUD BANG. 8, 12, 14, 17,28,38, Continue Take-off Accomplish stall/surge SURGE, SIMULATE LOUD NOISE, SUDDEN AIRCRAFT (repetitive) RTO to safe altitude checklist RECOVERABLE, SHUDDER, FLUCTUATION OF ENGINE N1/N2 Drop, EGT 47 not stabilizing W/PILOT PARAMETERS N1, N2, & EPR DECREASING, Increase, flight path INTERVENTION EGT INCREASING, TRAIN TO KEEP AIRCRAFT 51, 58 not CONTROL OF THE AIRCRAFT, CONTINUE VIBRATION, P0SSIBLE intervening to TAKEOFF, CLIMB TO A SAFE ALTITUE THEN YAW throttle back on THROTTLE BACK TO CLEAR SURGES AND dual engine event REAPPLY POWER AND TROUBLESHOOT 69, 70, 72, throttle PER CHECKLISTS good engine SURGE TAKEOFF < V1 LOUD BANG (usually 1 68, 57, Shutting RTO Contact Maintenance SURGE, NON- SIMULATE LOUD NOISE, SUDDEN or 2). down good engine RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 drop, EGT 54, 29 ENGINE PARAMETERS N1 & N2 & EPR increase, AIRCRAFT unsuccessful RTO DECREASE WHILE EGT INCREASES, TRAIN VIBRATION, YAW TO REJECT THE TAKEOFF

SURGE TAKEOFF > V1 LOUD BANG (usually 1 2, 3, 4, 16, 21, 22, Continue Take-off Accomplish stall/surge SURGE, NON- SIMULATE LOUD NOISE, SUDDEN or 2). 36, 45, 46, 48, 49, to safe altitude checklist RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 drop, EGT 52, 55,56, 60, 64, ENGINE PARAMETERS N1 & N2 & EPR increase, AIRCRAFT 76, 78, 80, RTO DECREASE WHILE EGT INCREASES, TRAIN VIBRATION, YAW 65, 63, 67 KEEP CONTROL OF THE AIRCRAFT AND shutdown/ throttle CLIMB TO A SAFE ALTITUDE BEFORE good engine ATTEMPTING TO TROUBLESHOOT. SURGE INITIAL CLIMB LOUD BANG (usually 1 15, 33, 41 Shutting Continue climb to Accomplish stall/surge SURGE, NON- SIMULATE LOUD NOISE, SUDDEN or 2). down good engine safe altitude checklist RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 drop, EGT ENGINE PARAMETERS N1 & N2 & EPR increase, AIRCRAFT DECREASE WHILE EGT INCREASES, TRAIN VIBRATION, YAW KEEP CONTROL OF THE AIRCRAFT AND CLIMB TO A SAFE ALTITUDE BEFORE ATTEMPTING TO TROUBLESHOOT SURGE CRUISE Quiet bang (possibly 9, 11, 13, 20,23, Stabilize flight Accomplish stall/surge SURGE, NON- SIMULATE LOUD NOISE, SUDDEN repetitive PARAMETER shut down good path checklist RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF FLUCTUATION (may engine ENGINE PARAMETERS N1 & N2 & EPR be only momentary), DECREASE WHILE EGT INCREASES, TRAIN AIRCRAFT TO KEEP CONTROL OF THE AIRCRAFT AND VIBRATION, CLIMB TO A SAFE ALTITUDE BEFORE ATTEMPTING TO TROUBLESHOOT

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GROUP 1

PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT PHASE Immediate Failure Mode Response POWER LOSS INITIAL CLIMB Bang or fire warning or 43, 27 Failure to Continue flight to evaluate, & perform SEVERE SIMULATE LOUD NOISE, SUDDEN AIRCRAFT single engine very severe vibration, stabilize flight path, achieve minimum appropriate checklist DAMAGE SHUDDER, FLUCTUATION OF ENGINE aircraft yaw, high EGT Shutting down safe altitude PARAMETERS N1 & N2 & EPR DECREASE good engine WHILE EGT INCREASES, TRAIN TO KEEP 32, 1, Not taking CONTROL OF THE AIRCRAFT AND CLIMB TO action to secure A SAFE ALTITUDE BEFORE ATTEMPTING engine TO TROUBLESHOOT POWER LOSS APPROACH Parameter spool down. 50, 44, 34, 30 Continue to land If go-round, evaluate FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine /LANDING Services (generators) Failing to control OR go-round as and perform FLIGHT DECK PANEL CHANGES FOR LOSS drop off line yaw or appropriate appropriate checklist OF SINGLE ENGINE. TRAIN RECOGNIZE THE compensate for SITUATION AND TO MAINTAIN AIRCRAFT reduced thrust CONTROL DURING LANDING OR GO- AROUND

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GROUP 2 PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT PHASE Immediate Failure Mode Response POWER LOSS GO-AROUND Parameter spool down. 10, 77 Failure to Continue flight to evaluate and perform FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine Yaw. Services recognize/ achieve minimum appropriate checklist FLIGHT DECK PANEL CHANGES FOR LOSS (generators) drop off compensate for safe altitude OF SINGLE ENGINE. TRAIN RECOGNIZE THE line power loss, SITUATION AND TO MAINTAIN AIRCRAFT airspeed too low CONTROL DURING LANDING OR GO- AROUND POWER LOSS TAKEOFF < V1 Bang or fire warning or 35 Not completing RTO Perform appropriate SEVERE SIMULATE LOUD NOISE, SUDDEN single engine very severe vibration, checklist, checklist. Contact DAMAGE AIRCRAFT SHUDDER, FLUCTUATION OF aircraft yaw, high EGT 81 Continuing Maintenance ENGINE PARAMETERS N1 & N2 & EPR takeoff, shutting DECREASE WHILE EGT INCREASES, TRAIN down wrong TO REJECT THE TAKEOFF engine SURGE INITIAL CLIMB LOUD BANG. 53, 71 Shutting Continue climb to Accomplish stall/surge SURGE, SIMULATE LOUD NOISE, SUDDEN AIRCRAFT (repetitive) down good engine safe altitude checklist RECOVERABLE, SHUDDER, FLUCTUATION OF ENGINE N1/N2 Drop, EGT W/PILOT PARAMETERS N1, N2, & EPR DECREASING, Increase, INTERVENTION EGT INCREASING, TRAIN TO KEEP AIRCRAFT CONTROL OF THE AIRCRAFT, CLIMB TO A VIBRATION, P0SSIBLE SAFE ALTITUE THEN THROTTLE BACK TO YAW CLEAR SURGES AND REAPPLY POWER AND TROUBLESHOOT PER CHECKLISTS SURGE GO-AROUND LOUD BANG (usually 1 19 Failure to Continue go- Accomplish stall/surge SURGE, NON- SIMULATE LOUD NOISE, SUDDEN or 2). stabilize flight path around to safe checklist RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 drop, EGT / coordinate crew altitude ENGINE PARAMETERS N1 & N2 & EPR increase, AIRCRAFT actions DECREASING WHILE EGT INCREASES. VIBRATION, YAW TRAIN TO KEEP CONTROL OF THE AIRCRAFT AND KEEP FLYING UNTILL AIRCRAFT IS AT A SAFE ALTITUDE BEFORE ATTEMPTING TO TROUBLESHOOT. POWER LOSS TAKEOFF > V1 Parameter spool-down. 37,6 Failing to Continue Take-off evaluate, & perform FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine Yaw, loss of control yaw/ to safe altitude appropriate checklist FLIGHT DECK DISPLAY FOR SUDDEN LOSS acceleration Services compensate for OF SINGLE ENGINE THRUST. TRAIN TO (generators) drop off reduced thrust MAINTAIN CONTROL OF AIRCRAFT line POWERLOSS INITIAL CLIMB Parameter spool down. 18 shut down good Continue flight. evaluate, & perform FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine Yaw, reduced climb rate engine Restart engine appropriate checklist FLIGHT DECK DISPLAY FOR SUDDEN LOSS Services (generators) OF SINGLE ENGINE THRUST. TRAIN TO drop off line MAINTAIN CONTROL OF AIRCRAFT POWERLOSS CRUISE Parameter spool down. 39 Failing to Continue flight evaluate, & perform FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine Yaw. Services control yaw, appropriate checklist FLIGHT DECK DISPLAY FOR SUDDEN LOSS (generators) drop off airplane upset as OF SINGLE ENGINE THRUST. TRAIN TO

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GROUP 2 PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT PHASE Immediate Failure Mode Response line result MAINTAIN CONTROL OF AIRCRAFT

SURGE CRUISE Quiet bang , 42 shut down good Stabilize flight Accomplish stall/surge SURGE, SIMULATE LOUD NOISE, SUDDEN PARAMETER engine path checklist RECOVERABLE, AIRCRAFT SHUDDER, FLUCTUATION OF FLUCTUATION (may W/PILOT ENGINE PARAMETERS N1 & N2 & EPR be only momentary), INTERVENTION DECREASING WHILE EGT AIRCRAFT INCREASES.TRAIN TO KEEP CONTROL OF VIBRATION, THE AIRCRAFT AND CLIMB TO A SAFE ALTITUDE BEFORE ATTEMPTING TO TROUBLESHOOT SURGE GO-AROUND LOUD BANG. 2 inability to Continue go- Accomplish stall/surge SURGE, SIMULATE LOUD NOISE, SUDDEN (repetitive) identify engine around to safe checklist RECOVERABLE, AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 Drop, EGT involved altitude W/PILOT ENGINE PARAMETERS N1 & N2 & EPR Increase, INTERVENTION DECREASING WHILE EGT INCREASES. AIRCRAFT TRAIN TO KEEP CONTROL OF THE VIBRATION, P0SSIBLE AIRCRAFT AND KEEP FLYING UNTILL YAW AIRCRAFT IS AT A SAFE ALTITUDE POWER LOSS CRUISE Bang or fire warning or 24 Shut down good Stabilize flight evaluate, & perform SEVERE SIMULATE LOUD NOISE, SUDDEN single engine very severe vibration, engine path appropriate checklist DAMAGE AIRCRAFT SHUDDER, SUSTAINED aircraft yaw, high EGT FLUCTUATION OF ENGINE PARAMETERS N1 & N2 & EPR DECREASING WHILE EGT INCREASES. TRAIN TO MAINTAIN CONTROL OF THE AIRCRAFT. Uncommanded TAKEOFF > V1 Aircraft yaw, engine 26 shut down good Control airplane evaluate, & perform No engine SIMULATE ENGINE PARAMETER thrust change or parameter difference engine direction. appropriate checklist damage INCREASE INTO WARNING BAND AND non-response to APPROPRIATE AIRCRAFT REACTION. throttle TRAIN TO CONTROL AIRCRAFT AND movement SECURE ENGINE BY FUEL CUTOFF.

ALSO SIMULATE SLOW ROLLBACK OR NON RESPONSE TO THROTTLE IN IFR CONDITIONS. TRAIN TO MAINTAIN AIRCRAFT CONTROL. Uncommanded INITIAL CLIMB Aircraft yaw, engine 74 Not recognizing Control airplane evaluate, & perform No engine SIMULATE THRUST INCREASE OR SLOW thrust change or parameter difference thrust direction. appropriate checklist damage ROLL BACK OR NON-RESPONSE TO non-response to asymmetry/yaw THROTTLE IN IFR CONDITIONS. TRAIN TO throttle until autopilot RECOGNISE AIRCRAFT SITUATION, FLY movement disconnect and THE AIRCRAFT, THEN APPRAISE ENGINE upset CONDITION 73 shut down good engine

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GROUP 2 PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT PHASE Immediate Failure Mode Response Uncommanded CRUISE Aircraft yaw, engine 59 Not recognizing Control airplane evaluate, & perform No engine SIMULATE THRUST INCREASE OR SLOW thrust change or parameter difference thrust asymmetry direction. appropriate checklist damage ROLL BACK OR NON-RESPONSE TO non-response to or yaw until THROTTLE IN IFR CONDITIONS TRAIN TO throttle autopilot RECOGNISE AIRCRAFT SITUATION, FLY movement disconnect and THE AIRCRAFT, THEN APPRAISE ENGINE upset CONDITION 31 shut down good engine Uncommanded DESCENT Aircraft yaw, engine 61 Not recognizing Control airplane evaluate, & perform No engine SIMULATE THRUST INCREASE OR SLOW thrust change or parameter difference thrust direction. appropriate checklist damage ROLL BACK OR NON-RESPONSE TO non-response to asymmetry/yaw THROTTLE IN IFR CONDITIONS. TRAIN TO throttle until autopilot RECOGNISE AIRCRAFT SITUATION THEN movement disconnect and FLY THE AIRCRAFT THEN APPRAISE upset ENGINE CONDITION. 25 shut down good engine Uncommanded APPROACH Aircraft yaw, engine 66, 79 shut down Control airplane SIMULATE THRUST INCREASE ON ONE thrust change or /LANDING parameter difference good engine direction. ENGINE. SIMULATE MAINTAIN non-response to engine non responsive DIRECTIONAL CONTROL AND SECURE throttle to PLA. ENGINE PER CHECKLISTS., movement FIRE WARNING TAKEOFF < V1 Fire warning (light, bell) RTO Perform FIRE No engine checklist. Contact damage Maintenance FIRE WARNING TAKEOFF > V1 Fire warning (light,) 40 RTO Continue flight to evaluate, & perform No engine achieve minimum FIRE checklist damage safe altitude FIRE WARNING INITIAL CLIMB Fire warning (light, bell) Shut down good Continue flight to evaluate, & perform No engine engine achieve minimum appropriate checklist damage safe altitude

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Table 2

PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT Immediate Failure Mode PHASE Response SURGE TAKEOFF < V1 LOUD BANG (usually 1 68, 57 Shutting RTO Contact Maintenance SURGE, NON- SIMULATE LOUD NOISE, SUDDEN or 2). down good engine RECOVERABLE AIRCRAFT SHUDDER, FLUCTUATION OF N1/N2 drop, EGT 54, 29 ENGINE PARAMETERS N1 & N2 & EPR increase, AIRCRAFT unsuccessful RTO SEVERE DECREASE WHILE EGT INCREASES. TRAIN VIBRATION, YAW 35, Not Completing DAMAGE TO REJECT THE TAKEOFF checklist, 81 Continuing takeoff, shutting down wrong engine SURGE TAKEOFF>V1 LOUD BANG. 8, 12, 14, 17, 28, Continue Take- Accomplish stall/surge SURGE, SIMULATE LOUD NOISE, SUDDEN INITIAL CLIMB (repetitive) N1/1n2 drop, 38 RTO off, climb, go checklist RECOVERABLE, AIRCRAFT SHUDDER, FLUCTUATION OF CRUISE EGT increase, 47 not stabilizing around to safe W/PILOT ENGINE PARAMETERS N1, N2, & EPR AIRCRAFT flight path altitude INTERVENTION DECREASING, EGT INCREASING, TRAIN TO GO AROUND VIBRATION. 51, 58 not KEEP CONTROL OF THE AIRCRAFT, POSSIBLE YAW intervening to CONTINUE TAKEOFF/GO AROUND, CLIMB throttle back on TO A SAFE ALTITUE THEN THROTTLE dual engine event BACK TO CLEAR SURGES AND REAPPLY 69, 70, 72 throttle POWER AND TROUBLESHOOT PER good engine. CHECKLISTS 42, 53, 71 shutting down good engine 2 Inability to identify engine involved POWER LOSS TAKEOFF>V1 Bang or fire warning or 43, 27 Failure to Maintain control evaluate, & perform SEVERE SIMULATE LOUD NOISE, AIRCRAFT single engine INITIAL CLIMB very severe vibration, stabilize flight path, of the aircraft, appropriate checklist DAMAGE SHUDDER, FLUCTUATION OF ENGINE CRUISE aircraft yaw, high EGT Shutting down Continue takeoff PARAMETERS N1 & N2 & EPR DESCENT good engine or climb to DECREASING WHILE EGT INCREASES. APPROACH 32, 1 Not taking achieve or TRAIN TO CONTINUE TO CONTROL THE action to secure maintain AIRCRAFT AND CLIMB AS NECESSARY TO engine. minimum safe A SAFE ALTITUDE BEFORE ATTEMPTING 24 Shut down good altitude TO TROUBLESHOOT. engine.

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PROBLEM SYMPTOM ICR Desired Next Response TRAINING ACTION FLIGHT Immediate Failure Mode PHASE Response POWERLOSS TAKEOFF > V1 Parameter spool down. 37, 6, 50, 44, 34, Continue takeoff, If go-round, evaluate FLAME OUT SIMULATE AIRCRAFT REACTION TO AND single engine CRUISE Services (generators) 30 Failing to go around, or and perform FLIGHT DECK PANEL CHANGES FOR LOSS APPROACH drop off line control yaw or landing as appropriate checklist OF SINGLE ENGINE. TRAIN TO MAINTAIN /LANDING compensate for appropriate CONTROL OF THE AIRCRAFT, THEN reduced thrust. 39 RECOGNISE SITUATION, Failing to control yaw, airplane upset as result. Uncommanded TAKEOFF >V1 Aircraft yaw, engine 74, 59, 61 Not Control airplane Evaluate and perform No engine SIMULATE THRUST INCREASE TO thrust change INITIAL CLIMB parameter difference. recognizing thrust direction appropriate checklist damage WARNING BAND AND APPROPRIATE or non- CRUISE asymmetry/yaw AIRCRAFT REACTION. TRAIN TO CONTROL response to DESCENT until autopilot AIRCRAFT AND SECURE ENGINE BY FUEL throttle disconnect and CUTOFF. movement aircraft upset resulted ALSO SIMULATE SLOW ROLL BACK OR 31, 25 Shut down NON-RESPONSE TO THROTTLE IN IFR good engine. CONDITIONS. TRAIN TO RECOGNISE AIRCRAFT SITUATION, FLY THE AIRCRAFT,

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Format of training material

It was recognized from the outset that training material should focus on the factual material to be trained and not on the training methodology. The material also needed to accommodate the following variables:

• Broad spectrum of pilot experience • Varying levels of interest in subject matter • Different learning styles • Variations in training aid technology • Training footprint available

The material was therefore structured to allow flexibility, as follows:

1. A video, highlighting the malfunctions most frequently causing problems. This could be viewed as part of recurrent training. 2. Text outlines (flashcards or cheat-sheets) for the malfunctions of greatest concern, giving a one-line description, symptoms, likely instrument behavior and typical appropriate pilot response. This could be used by all pilots as a quick reference, but might be most useful to the experienced pilot reluctant to read the entire text on malfunctions. 3. Text on a wider variety of engine malfunctions addressing some of the technical detail, at a high level. This could be used by all pilots as a reference source. 4. Introduction to the fundamentals of engine operation and installation (Engines 101), intended for use by the entry-level pilot to ensure a basic understanding. This material was beyond the scope of the PSM+ICR recommendations, but was specifically requested by airline representatives.

It was noted during the review process that much of the text material is very basic training. The text is intended to ensure that each pilot has at least a minimum level of understanding necessary to recognize and respond appropriately to propulsion system malfunctions; it is not intended for use by Flight Engineers or other propulsion specialists.

Although it is anticipated that the material will be useful outside North America, no attempt has been made to offer it in languages other than English. A video script has been provided to assist foreign operators or other groups with dubbing in other languages.

Preparation of Video

A video on engine surge/stall recognition had been produced by United Airlines and was made available to the group as the basis for a more comprehensive training video addressing a broader variety of engine malfunctions. Video clips of engines experiencing

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severe certification tests were provided by the CFMI, GE Aircraft Engines and Pratt & Whitney. These tests were intentionally selected to be as dramatic as possible, to show flight crews that engines can produce some very alarming symptoms and still remain airworthy, and that the flight crew should fly the airplane first, and attend to the engine problem when time permits. The symptoms shown in these video clips were therefore more severe than in the great majority of service events. Some service events have been even more severe, but video clips of such events were not available.

Although the video was prepared primarily with pilot training in mind, it would be beneficial for cabin crew to view it and to gain familiarity with the symptoms which an engine in distress may present, whilst still remaining safe.

It was intended that by addressing all of the malfunctions of primary concern in a single video, the likelihood of pilots seeing the whole package would be maximized. This did place constraints upon the detail which could be included in the video, since there was a general consensus that the interest of the audience would be lost after 15 or 20 minutes. Some material was suggested which could not be incorporated in the allotted time (or could not be readily located); specifically interviews with crew who had experienced engine malfunctions, and footage of the instruments as they might appear to the flight crew during the malfunction.

The script of the video is provided in Appendix 2.

Preparation of text

The team had initially been tasked to prepare generic text addressing engine malfunctions. However, it became apparent that additional text on basic engine operation would also be valuable and would avoid misunderstandings when discussing engine malfunctions.

The requirements of the target audience were difficult to agree upon – some pilots would want to explore technical details of malfunctions, others would prefer an overview which could be understood in a few minutes. The text on malfunctions is therefore presented in two formats; one with a wealth of detail, and the other as high-level summaries for quick reference.

It was suggested at one point that if pilots were having difficulty distinguishing engine malfunction symptoms from other events, the text should address such areas of confusion. This suggestion was not incorporated, since it was difficult to imagine all of the extraneous events which might present a similar symptom (e.g., a loud noise), and the value of doing so was not clear.

A copy of the text is provided in Appendix 3.

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Preparation of Simulator Package

One of the major shortfalls observed in many surge simulations was the unrealistic sound accompanying the engine surge. Considerable difficulty was experienced in obtaining a realistic recording of the surge sound, due to the high amplitude of the sound and the potential high cost of forcing an engine to surge. The following approaches were explored:

• CVR recordings involving engine surges were reviewed. The microphones appeared to saturate at the beginning of the surge, leading to a complete loss of signal for several seconds. • Videos of engine surge events at test facilities were reviewed. These were found to incorporate significant distortion of the sound caused by echoes from the surrounding test cell and ground. • A microphone and seat track accelerometer were installed on a GE flight test airplane which might experience engine stalls. High power stalls did indeed occur, but the microphone experienced some degree of signal clipping.

Work on defining the enhancements to the acoustic, engine parameter and airplane tactile yaw signatures response characteristics of a high power engine surge stall is not yet complete at the time of publication of this report. The industry team is developing and validating guidelines/requirements to assist operators in modifying existing "surge" simulations in order to provide a more realistic effect for training. In the interim, it is recommended that the acoustic signature be a loud bang, similar to close-range discharge of a shotgun. It is recognized that practical considerations may limit the volume of sound, such as distraction to training in neighboring simulators, but the volume used should be sufficient to "startle" the pilot. Similarly, the yaw input (for engines installed off the airplane ceneterline) should be a distinct jolt. Currently, the expected completion date is the end of 3rd quarter of 2001. This report will be revised upon completion of this work.

Human Factors Considerations

Three issues were identified: a) factors influencing the magnitude of the startle response to a compressor surge b) the simulator cues that might evoke that response c) the need for validating the effectiveness of the training pilots receive, both from the printed and audio/visual materials as well as from any enhanced simulation; e.g., LOFT that incorporates more realistic representations of engine malfunctions.

As the video notes, several factors influence the magnitude of the startle response pilots experience when the encounter a compressor surge or stall: 1) the magnitude of the impulse noise, 2) the fact that it is unexpected, and 3) that it occurs at a critical time (e.g., around V1). Although surges can and do occur at other times, the startle response is expected to be more disruptive when it occurs during a critical phase of flight when attention is focused and highly concentrated on a particular task. A true startle response

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results in observable, reflexive (non-voluntary) muscular contractions, and its principal impact on cognitive behavior is to induce a shift in attention to the noise that evoked the reaction.

The cues associated with a compressor surge were reviewed using flight test data as well as pilots' recollections of their own experience. The loud noise and airplane yaw were observed on the flight test data recording. The simulation group package is intended to improve the noise and yaw cues in surge simulations.

Vibration was not observed in the flight test data, which does not mean that vibration is never experienced during an engine surge – the nature of the engine failure would govern the degree of vibration felt. Previous work reported to the PSM+ICR group indicated that flight deck warnings could, in some cases, make the startle response more likely. A compressor surge accompanied by a fire warning was more likely to result in an RTO above V1 than a compressor surge without a flight deck warning.

Assuming enhanced simulation is incorporated into Level D devices, validating the effectiveness of training (from test and audio/visual materials developed to date) is a greater challenge, and one that will need additional effort to define the measures of pilot behavior that constitute a criterion of success, as well as to develop the scenarios that can test whether pilots react appropriately when they encounter unexpected engine malfunctions. Addressing the validation issue is left for proposed follow-on efforts.

The parameters shown on current engine monitoring displays are governed by FAR/JAR 25.1305, which was written with the expectation that a Flight Engineer would be available for monitoring engine health. As the industry has accrued experience in the behavior of turbine engines, and the duties of the flight engineer have been assumed by the pilots, the requirements of FAR/JAR25.1305 appear less appropriate. The concurrent incorporation of Fully Automated Digital Electronic Control (FADEC) systems on engines and the interest in health monitoring and prediction of incipient malfunctions has enabled the collection and processing of information not currently provided to the pilots. NASA has already conducted a number of studies on how engine monitoring displays might be improved. There is an opportunity for a significant improvement in the requirements and implementation of the engine information presented in flight.

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Recommendations

All operators should consider both the use of this video for recurrent training, and distribution of the text to all pilots, with a particular focus on entry-level pilots and those transitioning from turboprops.

Similar activity should be initiated to develop generic training materials for turboprop propulsion system malfunctions.

A review of recent PSM+ICR service experience should be undertaken in 2010, to audit the effectiveness of the training material and to establish whether further or different corrective action is required.

Activities to address the outstanding recommendations from the PSM+ICR committee, including development of human factors methodologies to validate training improvements, and review of the requirements for propulsion system instrumentation, should be initiated by the regulatory agencies and industry.

References

1.AIA/AECMA Project Report on Propulsion System Malfunction Plus Inappropriate Crew Response. 11/1/98

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Appendix 1 – Letter from ATA

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Appendix 2 – Video Script

Today’s jet transport engines are the most reliable and powerful aircraft engines ever developed. Over the past 40 years, technological improvements have increased the amount of thrust, improved fuel consumption, reduced noise, and reduced unwanted emissions. To accomplish these advances, internal engine pressure has been greatly increased on today’s high bypass turbo fan engines. The reliability of the gas turbine engine has reached a level where severe engine failure is so unlikely that most pilots will never experience one in their flying career. However modern turbine engines can still fail. And when they fail, whether with a loud bang and high vibration, or just quietly decay to zero thrust , the pilot is expected to recognize the specific engine problem and to then take appropriate action. Over the last several years, data has indicated some pilots have attempted to diagnose aircraft malfunctions prior to establishing control of the aircraft. This has occurred despite the fact that all pilots are taught to fly the aircraft first. So why does the data indicate that they have not done this? One of the main reasons is the startle factor. Because of modern aircraft’s high reliability, when a malfunction occurs it is frequently the first time the flight crew is exposed to the true sensations of that malfunction. While simulators have greatly improved pilot training, they have not always realistically simulated the actual noise, vibration and aerodynamic forces certain engine malfunctions cause. It also appears that the greater the physical sensations the pilot feels during the malfunction, the greater the startle factor, and the greater the likelihood the flight crew will try to diagnose the problem immediately instead of fly the aircraft first. When flight crews are interviewed after engine malfunction events, such as the surge of a large high bypass engine during initial climb out, they make very similar comments regarding the event. Pilots will often report that it felt like “a bomb went off” or that “the aircraft was falling apart”. The severity of the symptoms in some cases caused the flight crew to question the airworthiness of the aircraft and attempt to reject the take off above the V1 speed.

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Each time an event occurred, the sound and the feel of the event were different and often much more intense than indicated by any training the crews had received. Because of this, the flight crew either did not recognize the engine symptom,or was so concerned about the engine that they responded without taking time to correctly evaluate the situation. In each case, additional time spent in stabilizing the airplane’s flight path before responding to the engine symptom would have avoided a serious event. Remember, all transport category aircraft are designed and certified to be controllable with the most critical engine failed. Unlike early turboprops, turbofan powered airplanes do not require immediate pilot action to the engine in the event of a single engine malfunction or failure. Once the flight path is stabilized, the engine malfunction may be safely identified, and the appropriate checklists executed.

Taking the time to stabilize the flight path may sometimes lead to further engine damage, but despite that, the airplane still has the capability of safe flight. Engines are tested during initial certification, to demonstrate ruggedness following bird and ice ingestion. Even after a major failure, such as loss of an entire fan blade, which is an extremely rare event, the engine shuts down safely and the airplane is still airworthy. Service history of fleet aircraft verifies that there are generally no engine failures requiring an instant engine shutdown in order to maintain airplane safety and that continuing a takeoff after engine failure at V1 is safer than rejecting the takeoff.

So, the capability to recognize turbine engine malfunctions must be learned. But how? The objective of this video is to provide pilots with information to help them recognize and identify various engine malfunctions that have led to inappropriate crew responses and accidents in the past. These malfunctions include: • fire warnings, • tailpipe fires, • bird strikes,

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• vibration, • engine surge, • severe engine damage, • and slow power loss. In each case, the first priority is to employ the basic stick and rudder inputs necessary to maintain aerodynamic control of the aircraft. Remember, fly the airplane, and then identify and respond to the engine malfunction when time permits.

“Fire warnings” result from excessively high temperature in the space between the engine casings and cowling, or from fire detection system malfunctions. The heat source may be an actual fire around the engine, an engine failure allowing core air to escape through a hole in the casings, or a leak of hot air from a bleed duct. Whenever a fire warning occurs the first priority must be to fly the airplane. Once the airplane is stabilized, attention should then be directed toward execution of the appropriate checklist. Even if there is an actual fire, there is adequate isolation between the airplane structure and the nacelle to ensure sufficient time to establish and maintain airplane control to a safe altitude. Taking this time may cause further fire damage within the nacelle, but accident reports consistently show that flight path control must be focused on first, and it must remain a high priority until landing.

“Engine torching” or “tailpipe fires” mostly occur during an abnormal engine start, but they may also occur after shutdown, or during other ground operations. Although there may be no cockpit engine instrument indications, these events can be very spectacular when viewed from the ramp or cabin, and have been confused with an actual engine fire. The torching may be of short duration or it may last for several seconds. Note that the flame is confined to the tailpipe. Flames may turn upward and threaten the wing if no airflow is maintained through the engine. And in some cases an EGT increase may be indicated on the flight deck. Simply cutting fuel flow while continuing to motor the engine normally extinguishes the flames. The flight crew depends on ground personnel to identify engine torching.

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If you are told of an engine fire without any flight deck indications of a fire, follow the “engine torching” procedure as outlined in your flight manual. This procedure will direct you to motor the engine and extinguish the flames; the regular fire procedure will not. Do not perform the “engine fire” procedure unless a fire warning indication occurs, Executing the regular fire procedure may disable bleed air to the engine starter and prevent you from being able to motor the engine to blow out the tailpipe fire. There have been cases where flight attendants or passengers have initiated evacuations due to engine torching. These unnecessary evacuations can be minimized by prompt flight deck and cabin crew coordination to provide passengers with pertinent information and to alleviate their concerns.

“Bird strike” is a concern for every pilot. The birds may be observed by the flight crew, or the first indication of bird ingestion may be an engine surge. Flocking birds are a particular concern since they can affect more than one engine. It may be difficult to see the birds, and to know how many engines have ingested birds. Most bird strikes occur close to the ground, at the very time when there is least opportunity to appraise the situation. Nevertheless, the record shows that establishing flight path control first before taking action on the engine, is a more successful strategy than taking immediate action with the engine. There have been accidents resulting from bird-strike related Rejected Take Off’s above the V1 speed; and in each case, the airplane was in fact safe to fly. Therefore, rejecting a takeoff due to a bird strike at speeds above V1 is not considered to be appropriate. “Bird strike” by an engine may be accompanied by: • audible thuds, • vibration, • engine surge, • unpleasant odors , • and abnormal engine instrument readings such as high EGT. Throttling back an engine may be needed to clear a stall, after the airplane has been placed on a stable flight path. If the engine involved cannot be positively identified, do not shut it down. In

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the unlikely event of multiple engines surging, prompt action may be required to clear the stall on the engines one at a time, to assure that some power is available later. “Engine vibration” may be caused by a fan unbalance. This can come from ice buildup, fan blade material loss or aerodynamic excitation from fan blade distortion due to foreign object damage. Vibration can also come from internal engine failures, such as a bearing failure. Cross reference of all engine parameters will help to establish whether an engine failure actually exists. Engine induced vibration felt on the flight deck may not be indicated on instruments. For some engine failures, severe vibration may be experienced after the engine has been shut down, to the point where instruments are difficult to read. This vibration is caused by the unbalanced fan, windmilling at an engine speed close to an airframe’s natural resonance frequency, which amplifies the vibration. Changing airspeed and/or altitude will change the fan windmill speed and an airplane speed may be found where there will be much less vibration. There is no risk of airplane structural failure due to vibratory engine loads during this windmilling action.

From a flight crew members perspective one of the most startling events is the engine “surge” or “stall” on takeoff or during flight. An engine surge is, in the simplest terms, the breakdown of the airflow in a turbine engine. When the compressor blades stall they are no longer able to force the air through the engine from front to rear. Now the high pressure air in the middle of the engine can escape explosively from front and back simultaneously. Usually there are visible flames from both ends of the engine, accompanied with one or more very loud bangs. This violent airflow reversal will produce an instant loss of thrust and an immediate yaw that will literally spill most of the coffee from your cup. This yaw is accompanied by a vibration that cannot be duplicated in the simulator. Bird strikes, internal engine failures, engine pneumatic bleed malfunctions, or internal engine clearance changes can cause a surge. It is usually a problem in the compressor system and so is often referred to as a “compressor surge” or “compressor stall”. The magnitude of the symptoms, such as the loudness of the noise, and the severity of the vibration , vary with the power setting and the type of instability in the compression system. Low altitude and high power settings produce the loudest bangs with the most violent yaw and vibration. High altitude surges are

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frequently associated with engine power changes during leveling off or when initiating an altitude change. High altitude surges generally result in a muffled noise, light vibration, an increasing EGT, and may require power reduction to clear the condition. Some surges allow the engine to recover with no flight crew action, others recover after flight crew action to reduce power. The most severe surges are non recoverable. When the engine recovers by itself it is best to just fly the airplane and not interfere with the engine. Identification of a recoverable compressor surge or stall condition based on engine parameter fluctuations or changes alone can be difficult, due in part to the fact that the event is usually over in the blink of an eye. Generally most flight crews identify the condition as an engine malfunction when the EGT exceeds its limits or the EGT gage turns red. If EGT continues to rise following a surge the thrust lever should be retarded to allow the engine to recover. Then after the engine recovers power should be re-applied slowly. If the engine does not stall again when the power lever is re-advanced the power can be left high. If the engine stalls again with the re-application of power lever input, the power setting may need to be left at a low power or idle condition. Continue to fly the airplane, and ensure the indications return to normal. If the engine does not recover or the EGT remains out of limits, then a shutdown of the engine may be the logical choice depending on the operational situation. Your flight manual and checklists identify the specific procedures to follow. Remember that an engine at idle still provides power for airplane systems and creates less drag than if shut down. There have been numerous occasions where a high power compressor surge has occurred during the takeoff roll or initial climb out and the flight crew was notified by the tower that an engine was on fire. As a result the flight crews accomplished the engine fire checklist and shutdown the engine even though there was no fire warning annunciated in the cockpit. The tower saw fire out the inlet and tailpipe, and their information regarding seeing flames outside the engine was correct. But an engine shutdown was not necessary since this was not actually an aircraft fire. While the likelihood of a high power engine surge is rare, the startle factor associated with loud bangs and airplane vibration has lead to instances of inappropriate action such as: rejecting the

26 Draft report for PSM+ICR Phase 2 Turbofan work Appendix 2 07/17/09 takeoff after the V1 speed, shutting down the wrong engine, improperly executing the engine failure climb profile, or failing to comply with established ground tracks to clear rising terrain. Only take action to address the surge after stabilizing the flight path. Recent interviews with pilots who have experienced high power compressor surges during takeoff and initial climb have revealed that they initially thought that a bomb had exploded, or that they had hit a truck, or had a midair collision. Some pilots incorrectly interpreted the noise or bang as a tire failure. Remember, no matter how loud the bang, airplane control is always the first priority. In the event of a major internal engine failure resulting in “severe engine damage”, there may be a variety of symptoms on the flight deck: • fire warnings, • engine surge, • vibration, • high EGT, • fluctuating rpm, • oil system parameters out of limits, • and thrust loss. Any one of these symptoms alone could be from a more benign malfunction but multiple symptoms are a good indication of severe engine damage, and visual inspection by the cabin crew can be very helpful in confirming this. Visual symptoms may include flames, smoke, or visible damage to engine cowlings. It may not be possible to distinguish initially between an engine surge without damage, and one accompanying severe damage. The symptoms of the two kinds of events can be very similar and from an operational standpoint, it is not important to know immediately which of the two has occurred When in doubt, perform the surge procedure. If the engine does not recover, then it may have had severe damage. If it does become necessary to shut down the engine, wait until you positively identify the engine you select as actually being the malfunctioning engine. It should be noted that even an engine which may show signs of visible damage and visible flames, may very well be producing useful power necessary for initial climb out.

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Again, the first priority is to fly the airplane, not the engine. After you have positive control of the aircraft’s flight path, then identify and secure the affected engine when time permits. Diagnosis of exactly what caused the engine problem is neither necessary nor safe, if it diverts resources from flying the airplane.

The malfunctions discussed so far have had compelling cues, such as loud bangs, vibration, and warning or advisory messages. In each case, the challenge is to fly the airplane without being distracted by very compelling or alarming engine symptoms. The last type of malfunction to be discussed here is more subtle; “slow decay of thrust” or “non-response to power lever”. These can be subtle in fact to the point that it can be completely overlooked, with potentially serious consequences to the airplane. If an engine slowly reduces power , or when the thrust lever is moved the engine does not respond, then the airplane will experience asymmetric thrust. The problems will most likely develop at a point during the flight when the autopilot is engaged. The autopilot will compensate for the asymmetrical thrust on its own. It takes an alert flight crew to recognize the situation that is developing. If the airplane is badly miss trimmed when the autopilot is manually disconnected , or when the autopilot reaches the limits of its authority and automatically disconnects, only seconds remain before an unusual attitude is encountered. If no external visual references are available, such as flying over the water at night or in IMC, the likelihood of an upset increases. This condition of low power engine loss with the autopilot on has caused several aircraft upsets, which were not always recoverable. Flight control displacement or trim input indicators may be the only obvious indication that the autopilot is trimming the aircraft away from coordinated flight. Vigilance is required to detect these stealthy engine malfunctions and to maintain a safe flight attitude while the situation is still recoverable. But a slowly changing asymmetric thrust problem is not an easy one to detect. Symptoms may include multiple system problems, such as : • generators dropping off line, • low engine oil pressure, • unexplained airplane attitude changes, • significant differences between primary parameters from one engine to the next.

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If asymmetric thrust is suspected the pilot must be prepared to make immediate rudder or trim inputs to avoid an un-commanded aircraft roll. The first response must be to make the appropriate rudder input or trim adjustment. Disconnecting the autopilot without appropriate control input or trim adjustments, may result in a rapid roll maneuver. Different aircraft from different airframe manufacturers display different types of indicators to the pilot regarding the amount of trim the autopilot may be adding to the system. Consult your flight manual and training department to gain a full understanding of how your particular aircraft provides visual, audible, or tactile indications of the amount of trim being added by the autopilot.

The sequence of events and severity of symptoms experienced during an engine malfunction may vary from the events shown in this video, and from those experienced in a simulator. Engine malfunctions vary from one event to the next. The failures shown here were selected as relatively severe, but not the most severe that have ever occurred. Simulation of failures may be limited by simulator capability, which may not permit realistic levels of noise and vibration symptoms. Industry is currently addressing these concerns to enhance the simulation realism for such failures.

This video is intended to provide general information on the characteristics of some high bypass engine failures and malfunctions. It is not intended to be an in depth study of all possible engine failure modes. Specific remedial action to be taken in the event of an engine failure is published in the Airplane Flight or Operating Manual.

Appendix 3 – Text Airplane Turbofan Engine Operation and Malfunctions Basic Familiarization for Flight Crews

Chapter 1

General Principles

Introduction Propulsion Today's modern airplanes are powered by turbofan engines. These engines are quite reliable, providing years of trouble- free service. Because of the rarity of turbofan engine malfunctions and the limitations of simulating these malfunctions, many flight crews have felt unprepared to diagnose actual engine malfunctions that have occurred.

The purpose of this text is to provide straightforward material to help flight crews have the basics of airplane engine operational theory. This text will also provide pertinent Fig 1 showing balloon with no escape path for information about malfunctions that may be the air inside. All forces are balanced. encountered during the operation of turbofan- powered airplanes that cannot be simulated well Propulsion is the net force that results from and may cause the flight crew to be startled or unequal pressures. Gas (air) under pressure in a confused as to what the actual malfunction is. sealed container exerts equal pressure on all

surfaces of the container; therefore, all the forces While simulators have greatly improved pilot are balanced and there are no forces to make the training, many may not have been programmed container move. to simulate the actual noise, vibration and aerodynamic forces that certain malfunctions cause. In addition, it appears that the greater the sensations, the greater the startle factor, along with greater likelihood the flight crew will try to diagnose the problem immediately instead of flying the airplane.

It is not the purpose of this text to supersede or replace more detailed instructional texts or to suggest limiting the flight crew's understanding and working knowledge of airplane turbine engine operation and malfunctions to the topics Fig 2 showing balloon with released stem. and depth covered here. Upon completing this Arrow showing forward force has no opposing material, flight crews should understand that arrow. some engine malfunctions can feel and sound more severe than anything they have ever If there is a hole in the container, gas (air) cannot experienced; however, the airplane is still push against that hole and thus the gas escapes. flyable, and the first priority of the flight crew While the air is escaping and there is still should remain "fly the airplane." pressure inside the container, the side of the container opposite the hole has pressure against

it. Therefore, the net pressures are not balanced and there is a net force available to move the container. This force is called thrust.

The simplest example of the propulsion principle is an inflated balloon (container) where the stem is not closed off. The pressure of the air inside the balloon exerts forces everywhere inside the balloon. For every force, there is an opposite force, on the other side of the balloon, except on Fig 4 showing turbine engine as a cylinder of the surface of the balloon opposite the stem. turbomachinery with unbalanced forces pushing This surface has no opposing force since air is forward. escaping out the stem. This results in a net force that propels the balloon away from the stem. Components of a turbine engine The balloon is propelled by the air pushing on the FRONT of the balloon. The turbomachinery in the engine uses energy stored chemically as fuel. The basic principle of The simplest propulsion engine the airplane turbine engine is identical to any and all engines that extract energy from chemical The simplest propulsion engine would be a fuel. The basic 4 steps for any internal container of air (gas) under pressure that is open combustion engine are: at one end. A diving SCUBA tank would be such an engine if it fell and the valve was 1) Intake of air (and possibly fuel) knocked off the top. The practical problem with 2) Compression of the air (and possibly fuel) such an engine is that, as the air escapes out the 3) Combustion, where fuel is injected (if it was open end, the pressure inside the container would not drawn in with the intake air) and burned to rapidly drop. This engine would deliver convert the stored energy- propulsion for only a limited time. 4) Expansion and exhaust, where the converted energy is put to use. The turbine engine These principles are exactly the same ones that A turbine engine is a container with a hole in the make your lawn mower or automobile engine go. back end (tailpipe or nozzle) to let air inside the container escape, and thus provide propulsion. In the case of a piston engine such as the engine Inside the container is turbomachinery to keep in your car or lawn mower, the intake, the container full of air under constant pressure. compression, combustion, and exhaust steps occur in the same place (cylinder head) at different times as the piston goes up and down.

In the turbine engine, however, these same four steps occur at the same time but in different places. As a result of this fundamental difference, the turbine has engine sections called:

1) The inlet section 2) The compressor section Fig 3 showing our balloon with machinery in 3) The combustion section front to keep it full as air escapes out the back 4) The exhaust section. for continuous thrust. The practical axial flow turbine engine

The turbine engine in an airplane has the various sections stacked in a line from front to back. As a result, the engine body presents less drag to the airplane as it is flying. The air enters the front of the engine and passes essentially straight through from front to back. On its way to the back, the

air is compressed by the compressor section. airfoils, called blades, set at an angle to the disk Fuel is added and burned in the combustion rim. Each blade is close to the shape of a section, then the air is exhausted through the exit miniature propeller blade, and the angle at which nozzle. it is set on the disk rim is called the angle of attack. This angle of attack is similar to the pitch The laws of nature will not let us get something of a propeller blade or an airplane wing in flight. for nothing. The compressor needs to be driven As the disk with blades is forced to rotate by the by something in order to work. Just after the turbine, each blade accelerates the air, thus burner and before the exhaust nozzle, there is a pumping the air behind it. The effect is similar turbine that uses some of the energy in the to a household window fan. discharging air to drive the compressor. There is a long shaft connecting the turbine to the After the air passes through the blades on a disk, compressor ahead of it. the air will be accelerated rearward and also forced circumferentially around in the direction of the rotating Compressor combustor turbine nozzle

Fig 5 showing basic layout of jet propulsion system.

Machinery details Fig 6 showing compressor rotor disk.

From an outsider's view, the flight crew and disk. Any tendency for the air to go around in passengers rarely see the actual engine. What is circles is counterproductive, so this tendency is seen is a large elliptically-shaped pod hanging corrected by putting another row of airfoils from the wing or attached to the airplane behind the rotating disk. This row is stationary fuselage toward the back of the airplane. This and the airfoils are at an opposing angle. pod structure is called the nacelle or cowling. The engine is inside this nacelle. What has just been described is a single stage of compression. Each stage consists of a rotating The first nacelle component that incoming air disk with many blades on the rim, called a rotor encounters on its way through an airplane turbine stage, and, behind it, another row of airfoils that engine is the inlet cowl. The purpose of the inlet is not rotating, called a stator. Air on the cowl is to direct the incoming air evenly across backside of this rotor/stator pair is accelerated the inlet stages of the engine. The shape of the rearward, and any tendency for the air to go interior of the inlet cowl is very carefully around circumferentially is corrected. designed to guide this air.

The compressor of an airplane turbine engine has quite a job to do. The compressor has to take in an enormous volume of air and compress it to 1/10th or 1/15th of the volume it had outside the engine. This volume of air must be supplied continuously, not in pulses or periodic bursts.

The compression of this volume of air is accomplished by a rotating disk containing many

Fig 8 showing layout of a dual rotor airplane turbine engine.

Most of today's turbine engines are dual-rotor engines, meaning there are two distinct sets of rotating components. The rear compressor, or high-pressure compressor, is connected by a hollow shaft to a high-pressure turbine. This is the high rotor. In some literature, the rotors are called spools, such as the "high spool." In this text, we will use the term rotor. The high rotor is often referred to as N2 for short.

Fig 7 showing 9 stages of a compressor rotor assembly. The front compressor, or low-pressure compressor, is in front of the high-pressure A single stage of compression can achieve compressor. The turbine that drives the low- perhaps 1.5:1 or 2.5:1 decrease in the air's pressure compressor is behind the turbine that volume. In order to achieve the 10:1 to 15:1 drives the high-pressure compressor. The low- total compression needed for the engine to pressure compressor is connected to the low- develop adequate power, the engine is built with pressure turbine by a shaft that goes through the many stages of compressors stacked in a line. hollow shaft of the high rotor. The low-pressure Depending upon the engine design, there may be rotor is called N1 for short. 10 to 15 stages in the total compressor. The N1 and N2 rotors are not connected As the air is compressed through the compressor, mechanically in any way. There is no gearing the air increases in velocity, temperature, and between them. As the air flows through the pressure. Air does not behave the same at engine, each rotor is free to operate at its own elevated temperatures, pressures, and velocities efficient speed. These speeds are all quite as it does toward the front of the engine before it precise and are carefully calculated by the is compressed. In particular, this means that the engineers who designed the engine. The speed speed that the compressor rotors must have at the in RPM of each rotor is often displayed on the back of the compressor is different than at the engine flight deck and identified by gages or front of the compressor. If we had only a few readouts labeled N1 RPM and N2 RPM. Both stages, this difference could be ignored; but, for rotors have their own redline limits. 10 to 15 stages of compressor, it would not be efficient to have all the stages go at the same The turbofan engine rotating speed.

The most common solution to this problem is to break the compressor in two. This way, the front 4 or 5 stages can rotate at one speed, while the rear 6 or 7 stages can rotate at a different, higher, speed. To accomplish this, we also need two separate turbines and two separate shafts.

Fig 9 showing schematic of fan jet engine. In this sketch, the fan is the low-pressure compressor. In some engine designs, there will be a few stages of low-pressure compressor with the fan. These may be called booster stages.

The fan is not like a propeller. On a propeller, In some engine designs, the N1 and N2 rotors each blade acts like an airplane wing, developing may rotate in opposite directions, or there may lift as it rotates. The "lift" on a propeller blade be three rotors instead of two. Whether or not pulls the engine and airplane forward through the these conditions exist in any particular engine are air. engineering decisions and are of no consequence to the pilot. In a turbofan engine, thrust is developed by the A turbofan engine is simply a turbine engine fan rotor system, which includes the static where the first stage compressor rotor is larger in structure (fan exit guide vanes) around it. The diameter than the rest of the engine. This larger fan system acts like the open balloon in our stage is called the fan. The air that passes example at the start of this discussion, and thus through the fan near its inner diameter also pushes the engine, and the airplane along with it, passes through the remaining compressor stages through the air from the unbalanced forces. in the core of the engine and is further compressed and processed through the engine What the fan and the propeller have in common cycle. The air that passes through the outer is that the core engine drives them both. diameter of the fan rotor does not pass through the core of the engine, but instead passes along LESSON SUMMARY the outside of the engine. This air is called bypass air, and the ratio of bypass air to core air So far we have learned: is called the bypass ratio. 1) Propulsion is created by the unbalance of The air accelerated by the fan in a turbofan forces. engine contributes significantly to the thrust 2) A pressure vessel with an open end delivers produced by the engine, particularly at low propulsion due to the unbalance of forces. forward speeds and low altitudes. In large 3) An airplane propulsion system is a pressure engines such as the engines that power the B747, vessel with a open end in the back. B757, 4) An airplane engine provides a constant supply of air for the pressure vessel. 5) An airplane turbine engine operates with the same 4 basic steps as a lawnmower or automobile engine. 6) An airplane turbine engine has sections that perform each of the 4 basic steps of intake, compression, combustion, and exhaust. 7) Compression is accomplished by successive stages of rotor/stator pairs. 8) The compressor stages are usually split into low-pressure and high-pressure compressor sections. 9) The low-pressure section can be referred to as N1 and the high-pressure section can be referred to as N2. 10) A fan is the first stage of compression where the rotor and its mating stator are larger in diameter than the rest of the engine.

Fig 10 showing schematic of a turboprop. In this configuration, there are two stages of turbine with a shaft that goes through the engine to a gearbox which reduces the rotor speed of the propeller.

B767, A300, A310, etc., as much as three- quarters of the thrust delivered by the engine is developed by the fan.

Chapter 2

Engine systems

From an engineer's point of view, the turbofan The accessory drive gearbox is most often engine is a finely-tuned piece of mechanical attached directly to the outside cases of the equipment. In order for the engine to provide engine at or near the bottom. The accessory adequate power to the airplane at a weight that drive gearbox is driven by a shaft that extends the airplane can accommodate, the engine must directly into the engine and it is geared to one of operate at the limit of technical feasibility. At the compressor rotors of the engine. Usually, it the same time, the engine must provide reliable, is driven by the high-pressure compressor. safe and economical operation.

Within the engine, there are systems that keep everything functioning properly. Most of these systems are transparent to the pilot. For that reason, this text will not go into deep technical detail. While such discussion would be appropriate for mechanics training to take care of the engine, it is the purpose of this text to provide information that pilots can use in understanding the nature of some engine malfunctions that may be encountered during flight.

The systems often found associated with the Fig 11 showing typical accessory drive gearbox. operation of the engine are: The gearbox has attachment pads on it for 1) The accessory drive gearbox accessories that need to be mechanically driven. 2) The fuel system These accessories include airplane systems, such 3) The lubrication system as generators for airplane and necessary engine 4) The ignition system electrical power, and the hydraulic pump for 5) The bleed system airplane hydraulic systems. Also attached to the 6) The start system gearbox are the starter and the fuel pump/fuel 7) The anti-ice system. control.

In addition, there are airplane systems that are Fuel system powered or driven by the engine. These systems may include: The fuel system associated directly with the propulsion system consists of: 1) Electrical system 2) Pneumatic system 1) A fuel pump 3) Hydraulic system 2) A fuel control 4) Air conditioning system. 3) Fuel manifolds 4) Fuel nozzles These airplane systems are not associated with 5) A fuel filter continued function of the engine or any engine 6) Heat exchangers malfunctions, so they will not be discussed in 7) Drains this text. The airplane systems may provide cues 8) A pressurizing and dump valve. for engine malfunctions that will be discussed in the chapter on engine malfunctions. All are external to the engine except the fuel nozzles. Accessory drive gearbox The airplane fuel system supplies pressurized fuel from the main tanks. The fuel is pressurized

by electrically-driven boost pumps in the tanks Fig 12 characterizing that the fuel control is an and then flows through the spar valve or LP "intelligent" component that does the work once shut-off valve to the engine LP fuel pump inlet. the flight crew "tells it what to do."

The fuel pump is physically mounted on the automatically meters the fuel to the fuel nozzles gearbox. Most engine fuel pumps have two within the engine at the required rate to achieve stages, or, in some engines, there may actually be the power requested by the flight crew. A fuel two separate pumps. There is an LP (low- flow meter measures the fuel flow sent to the pressure) stage that increases fuel pressure so engines by the control. that fuel can be used for servos. At this stage, the fuel is filtered to remove any debris from the In older engines, the fuel control is airplane tanks. Following the LP stage, there is hydromechanical, which is a technical way of an HP (high-pressure) stage that increases fuel saying that it operates directly from pressure and pressure above the combustor pressure. The HP mechanical speed physically input into the pump always provides more fuel than the engine control unit. needs to the fuel control, and the fuel control meters the required amount to the engine and On newer airplanes, control of the fuel metering bypasses the rest back to the pump inlet. is done electronically by a computer device called by names such as "EEC" or "FADEC." The fuel delivered from the pump is generally EEC stands for Electronic Engine Control, and used to cool the engine oil and IDG oil on the FADEC stands for Full Authority Digital Engine way to the fuel control. Some fuel systems also Control. The net result is the same. Electronic incorporate fuel heaters to prevent ice crystals controls have the capability of more precisely accumulating in the fuel control during low- metering the fuel and sensing more engine temperature operation and valves to bypass those operating parameters to adjust fuel metering. heat exchangers depending on ambient This results in greater fuel economy and more temperatures. reliable service.

The fuel control is installed on the engine either The fuel nozzles are deep within the engine in on the accessory gearbox, or directly to the fuel the combustion section right after the pump, or, in the case of an electronic control, to compressor. The fuel nozzles provide a the engine cases. The purpose of the fuel control precisely-defined spray pattern of fuel mist into is to provide the required amount of fuel to the the combustor for rapid, powerful, and complete fuel nozzles at the requested time. The rate at combustion. It is easiest to visualize the fuel which fuel is supplied to the nozzles determines nozzles as being similar to a showerhead. the acceleration or deceleration of the engine. The fuel system also includes drains to safely The flight crew sets the power requirements by dispose of the fuel in the manifolds when the moving a thrust lever in the flight deck. When engine is shut down, and, in some engines, to the flight crew adjusts the thrust lever, however, conduct leaked fuel overboard. they are actually "telling the control" what power is desired. The fuel control senses what the Lubrication system engine is doing and An airplane turbine engine, like any engine, must be lubricated in order for the rotors to turn easily without generating excessive heat. Each rotor system in the engine has, as a minimum, a rear and front bearing to support the rotor. That means that the N1 rotor has two bearings and the N2 rotor has two bearings for a total of 4 main bearings in the engine. There are some engines or older engines that have intermediate and/or special bearings; however, the number of bearings in a given engine is usually of little direct interest to a basic understanding of the engine.

The lubrication system of a turbine engine any reason, the loss of power would be serious. includes: With continuous ignition, combustion will restart automatically, probably without the pilot even 1) An oil pump noticing that there was an interruption in power. 2) An oil storage tank 3) A delivery system to the bearing Some engines, instead of having continuous compartments (oil lines) ignition, monitor the combustion process and 4) Lubricating oil jets within the bearing turn the igniters on as required, thus avoiding the compartments need for continuous ignition. 5) Seals to keep the oil in and air out of the compartments The ignition system includes: 6) A scavenge system to remove oil from the bearing compartment after the oil has done its 1) Igniter boxes which transform low-voltage job. After the oil is scavenged, it is cooled by Alternating Current (AC) from either a gearbox- heat exchangers, and filtered mounted alternator or from the airplane, into 7) Oil quantity, pressure, temperature, gages and high-voltage Direct Current (DC) filter bypass indications on the flight deck for 2) Cables to connect the igniter boxes to the monitoring of the oil system igniter plugs 8) Oil filters 3) Ignitor plugs. 9) Heat exchangers. Often one exchanger serves as both a fuel heater and an oil cooler For redundancy, the ignition system has two 10) Chip detectors, usually magnetic, to collect igniter boxes and two igniter plugs per engine. bearing compartment particles as an indication of Only one igniter in each engine is required to bearing compartment distress. Chip detectors light the fuel in the combustor. Some airplanes may trigger a flight deck indication or be allow the pilot to select which igniter is to be visually examined during line maintenance used; others use the engine control to make the 11) Drains to safely dispose of leaked oil selection. overboard. Bleed system The gages in item 7 are the window that the flight crew has to monitor the health of the Stability bleeds lubrication system. The compressors of airplane turbine engines are Ignition system designed to operate most efficiently at cruise. Without help, these compressors may operate The ignition system is a relatively very poorly or not at all during starting, at very straightforward system. Its purpose is to provide low power, or during rapid transient power the spark within the combustion section of the changes, conditions when they are not as engine so that, when fuel is delivered to the fuel efficient. To reduce the workload on the nozzles, the atomized fuel mist will ignite and compressor during these conditions, engines are the combustion process will start. equipped with bleeds to discharge large volumes of air from the compressor before it is fully Since all 4 steps of the engine cycles in a turbine compressed. engine are continuous, once the fuel is ignited the combustion process normally continues until The bleed system usually consists of: the fuel flow is discontinued during engine shutdown. This is unlike the situation in a piston 1) Bleed valves engine, where there must be an ignition spark 2) Solenoids or actuators to open and close the each time the combustion step occurs in the bleed valves piston chamber. 3) A control device to signal the valves when to open and close Turbine engines are provided with a provision on 4) Lines to connect the control device to the the flight deck for "continuous ignition." When actuators. this setting is selected, the ignitor will produce a spark every few seconds. This provision is In older engines, a control device measures the included for those operations or flight phases pressure across one of the engine compressors, where, if the combustion process were to stop for compares it to the inlet pressure of the engine,

and directs higher-pressure, high-compressor air to an air piston-driven actuator at the bleed valve A pneumatic starter is mounted on the accessory to directly close the valve. In newer engines, the gearbox, and is powered by air originating from electronic fuel control determines when the bleed another engine, from the APU, or from a ground valves open and close. cart. A start valve controls the input selection. The starter drives the accessory gearbox, which Generally, all the compressor bleed valves are drives the high-compressor rotor via the same open during engine start. Some of the valves drive shaft normally used to deliver power TO close after start and some remain open. Those the gearbox. that remain open then close during engine acceleration to full power for takeoff. These Fuel flow during starting is carefully scheduled valves then remain closed for the duration of the to allow for the compressor's poor efficiency at flight. very low RPM, and bleeds are used to unload the compressor until it can reach a self-sustaining If, during in-flight operation, the fuel control speed. During some points in a normal engine senses instability in the compressors, the control start, it may even look as if the engine is not may open some of the bleed valves momentarily. accelerating at all. After the engine reaches the This will probably be completely unnoticed by self-sustaining speed, the starter de-clutches the flight crew except for an advisory message from the accessory gearbox. This is important, on the flight deck display for some airplane as starters can be damaged with exposure to models. extended, high-speed operation. The engine is able to accelerate up to idle thrust without further Cooling/clearance control bleeds assistance from the starter.

Air is also extracted from the compressor, or the The starter can also be used to assist during in- fan airflow, for cooling engine components and flight restart, if an engine must be restarted. At for accessory cooling in the nacelle. In some higher airspeeds, the engine windmill RPM may engines, air extracted from the compressor is be enough to allow engine starting without use of ducted and squirted on the engine cases to the pneumatic starter. The specific Airplane control the clearance between the rotor blade tips Flight Manual should be consulted regarding the and the case wall. Cooling the case in this way conditions in which to perform an in-flight shrinks the case closer to the blade tips, restart. improving compression efficiency. Anti-ice system Service bleeds An airplane turbine engine needs to have some The engines are the primary source of protection against the formation of ice in the pressurized air to the airplane for cabin inlet and some method to remove ice if ice does pressurization. In some airplanes, engine bleed form. The engine is equipped with the capability air can be used as an auxiliary power source for to take some compressor air, via a bleed, and back-up hydraulic power air-motors. Air is duct it to the engine inlet or any other place taken from the high compressor, before any fuel where anti-ice protection is necessary. Because is burned in it, so that it is as clean as the outside the compressor bleed air is quite hot, it prevents air. The air is cooled and filtered before it is the formation of ice and/or removes already- delivered to the cabins or used for auxiliary formed ice. power. On the flight deck, the flight crew has the capability to turn anti-ice on or off. There is Start system generally no capability to control the amount of anti-ice delivered; for example, "high," When the engine is stationary on the ground, it "medium" or "low." Such control is not needs an external source of power to start the necessary. compressor rotating so that it can compress enough air to get energy from the fuel. If fuel were lit in the combustor of a completely non- rotating engine, the fuel would puddle and burn without producing any significant airflow rearward.

Chapter 3

Engine instrumentation in the flight deck

Airplanes in service today are equipped with devices available to the flight crew that provide feedback information about the engine to set engine power and monitor the condition of the engine. In older airplanes, these devices were gages on the panel. In newer airplanes, the airplane is equipped with electronic screens Rotor RPM. On an airplane equipped with a which produce computer-generated displays that multiple-rotor turbine engine, there will be a resemble the gages that used to be on the panel. rotor speed indication for each rotor. The N1 Whether gages or electronic displays are used, gage will provide the rotor speed of the low- the information given to the flight crew is the pressure rotor and the N2 (or N3 for a 3-rotor same. engine) gage will provide the rotor speed of the high-pressure rotor. N1 is a certified thrust- The gages are most useful when considered in setting parameter. context with each other, rather than considering one gage in isolation. The units of rotor speed are Revolutions Per Minute or RPM, but rotor speed is indicated as a What follows is a brief description of the gages non-dimensional ratio – that of engine rotor and what information they provide. speed as compared to some nominal 100% speed representing a high-power condition (which is not necessarily the maximum permissible speed). Engine operating manuals specify a maximum operational limit RPM or redline RPM that will generally be greater than 100 percent.

Low N1 may indicate engine rollback or flameout, or severe damage such as LP turbine Engine Pressure Ratio or EPR. Engine failure. Rapid N1 fluctuations may be caused by pressure ratio is a measure of thrust provided by engine operational instability such as surge. the engine. EPR indicators provide the ratio of Higher rotor speeds will be required at high the pressure of the air as it comes out of the altitudes to achieve takeoff-rated thrust. turbine to the pressure of the air as it enters the Unexpectedly high N1 may indicate a fuel compressor. EPR is a certified thrust-setting control malfunction. parameter. Some engine manufacturers recommend that engine power management be N2 is used for limit monitoring and condition performed by reference to EPR. monitoring. On older engines, it is also used to monitor the progress of engine starting and to Low EPR reading may be caused by engine select the appropriate time to start fuel flow to rollback or flameout, or internal damage such as the engine. an LP turbine failure. Rapid EPR fluctuations may be caused by engine operational instability such as surge, or rapidly-changing external conditions such as inclement weather or bird ingestion. Unexpectedly high EPR may indicate a fuel control malfunction, or malfunction or clogging of the inlet air pressure probes.

Exhaust Gas Temperature or EGT. Exhaust gas temperature is a measure of the temperature of the gas exiting the rear of the engine. It is measured at some location in the turbine. Since

the exact location varies according to engine reading reflects the actual pressure of the oil as it model, EGT should not be compared between is delivered to the bearing compartments. Oil engine models. Often, there are many sensors at system parameters historically give false the exit of the turbine to monitor EGT. The indications of a problem as frequently as the oil indicator on the flight deck displays the average system has a genuine problem, so crosschecking of all the sensors. with the other oil system indications is advisable.

High EGT can be an indication of degraded Low oil pressure may result from pump failure, engine performance. Deteriorated engines will from a leak allowing the oil system to run dry, be especially likely to have high EGT during from a bearing or gearbox failure, or from an takeoff. indication system failure. High oil pressure may be observed during extremely low temperature EGT is also used to monitor engine health and operations, when oil viscosity is at a maximum. mechanical integrity. Excessive EGT is a key indicator of engine stall, of difficulty in engine Low Oil Pressure Caution. Generally, if the oil starting, of a major bleed air leak, and of any pressure falls below a given threshold level, an other situation where the turbine is not extracting indication light or message is provided to draw enough work from the air as it moves aft (such as attention to the situation. severe engine damage).

There is an operational limit for EGT, since excessive EGT will result in turbine damage. Operational limits for EGT are often classified as time-at-temperature.

Oil Temperature Indicator. The Oil temperature indicator shows the oil temperature at some point in the lubrication circuit, although this point differs between engine models.

Elevated oil temperatures indicate some Fuel Flow indicator. The fuel flow indicator unwanted source of heat in the system, such as a shows the fuel flow in pounds (or kilograms) per bearing failure, sump fire or unintended leakage hour as supplied to the fuel nozzles. Fuel flow is of high temperature air into the scavenge system. of fundamental interest for monitoring in-flight High oil temperature may also result from a fuel consumption, for checking engine malfunction of the engine oil cooler, or of the performance, and for in-flight cruise control. valves scheduling fluid flow through the cooler.

High fuel flow may indicate a significant leak Oil Quantity Indicator. The oil quantity between the fuel control and fuel nozzles, indication monitors the amount of oil in the tank. particularly if rotor speeds or EPR appear normal This can be expected to vary with power setting, or low. since the amount of oil in the sumps is a function of rotor speed.

A steady decrease in oil quantity may indicate an oil leak. There is likely to still be some usable oil in the tank even after the oil quantity gage reads zero, but the oil supply will be near exhaustion and a low pressure indication will soon be seen. A large increase in the oil quantity Oil Pressure Indicator. The oil pressure may be due to fuel leaking into the oil system, indicator shows the pressure of the oil as it and should be investigated before the next flight. comes out of the oil pump. In some cases, the Flight crews should be especially vigilant to oil pressure reading system takes the bearing check other oil system indications before taking compartment background pressure, called action on an engine in-flight solely on the basis breather pressure, into account so that the gage of low oil quantity.

Oil Filter Bypass Indication. If the oil filter Fire Warning Indicators. Each engine has a becomes clogged with debris (either from dedicated fire warning indication, which may contamination by foreign material or debris from cover multiple fire zones and may address lesser a bearing failure), the pressure drop across the degrees of high undercowl temperature (using filter will rise to the point where the oil bypasses messages such as “Engine Overheat”). the filter. This is announced to the pilot via the oil filter impending bypass indication. This indication may go away if thrust is reduced (because oil flow through the filter and pressure drop across the filter are reduced).

Fuel Filter Impending Bypass. If the fuel filter at the engine fuel inlet becomes clogged, an Fuel Inlet Pressure Indicator. The fuel inlet impending bypass indication will alert the crew pressure indicator measures the pressure at the for a short while before the filter actually goes inlet to the engine-driven fuel pump. This into bypass. pressure will be the pressure of the fuel supplied from the airplane. Fuel Heat Indication. The fuel heat indicator registers when the fuel heat is on. Fuel heat indicators are not needed for engines where fuel heating is passively combined with oil cooling, and no valves or controls are involved.

Engine Starter Indication. During assisted starting, the start valve will be indicated open until starter disconnect. The position of the start Air Temperature Indicator. This gage is not switch shows the starter status (running or an actual engine gage, but rather is an airplane disconnected). If the starter does not disconnect gage. The air temperature indicator provides the once the engine reaches idle, or if it disconnects temperature of the air outside the airplane. This but the starter air valve remains open, the starter temperature may be recorded from specific will fail when the engine is at high power, locations and, therefore, the actual value may potentially damaging other systems. More mean different things depending upon the recent engine installations may also have particular airplane. This temperature typically is advisory or status messages associated with used to help select EPR in those engines where engine starting. thrust is set by EPR.

Vibration Indication. A vibration gage In addition to the above indications, recently- indicates the amount of vibration measured on designed airplanes have a wide variety of the engine LP rotor and/or HP rotor. Vibration is caution, advisory and status messages that may displayed in non-dimensional units, and is used be displayed in the event of an engine for condition monitoring, identification of the malfunction or abnormal operation. Since these affected engine after foreign object ingestion, are specific to each particular airplane design, and detection of fan unbalance due to icing. The they cannot be addressed here; reference to the level of vibration will change with engine speed. appropriate Airplane Flight or Operations Manual will provide further information. Powerplant Ice Protection Indication. If anti- icing is selected, an indication is provided (such as wing anti-ice or nacelle anti-ice).

Thrust Reverser Indication. Typically, dedicated thrust reverser indications are provided to show thrust reverser state: deployed, in transit, and/or fault indications and messages. The exact indications are installation-specific and further details may be obtained from the Airplane Flight or Operations Manual.

Chapter 4

Engine Malfunctions

To provide effective understanding of and simultaneously in different places in the engine. preparation for the correct responses to engine The part of the cycle susceptible to instability is in-flight malfunctions, this chapter will describe the compression phase. turbofan engine malfunctions and their consequences in a manner that is applicable to In a turbine engine, compression is accomplished almost all modern airplane turbofan-powered aerodynamically as the air passes through the aircraft. These descriptions, however, do not stages of the compressor, rather than by supersede or replace the specific instructions that confinement, as is the case in a piston engine. are provided in the Airplane Flight Manual and The air flowing over the compressor airfoils can appropriate checklists. stall just as the air over the wing of an airplane can. When this airfoil stall occurs, the passage Compressor surge of air through the compressor becomes unstable and the compressor can no longer compress the It is most important to provide an understanding incoming air. The high-pressure air behind the of compressor surge. In modern turbofan stall further back in the engine escapes forward engines, compressor surge is a rare event. If a through the compressor and out the inlet. compressor surge (sometimes called a compressor stall) occurs during high power at takeoff, the flight crew will hear a very loud bang, accompanied by yaw and vibration. The bang will likely be far beyond any engine noise, or other sound, the crew may have previously experienced in service.

Compressor surge has been mistaken for blown tires or a bomb in the airplane. The flight crew may be quite startled by the bang, and, in many cases, this has led to a rejected takeoff above V1. These high-speed rejected takeoffs have sometimes resulted in injuries, loss of the airplane and even passenger fatalities.

The actual cause of the loud bang should make This escape is sudden, rapid and often quite no difference to the flight crew’s first response, audible as a loud bang similar to an explosion. which should be to maintain control of the Engine surge can be accompanied by visible airplane and, in particular, continue the takeoff if flames forward out the inlet and rearward out the the event occurs after V1. Continuing the tailpipe. Instruments may show high EGT and takeoff is the proper response to a tire failure EPR or rotor speed changes, but, in many stalls, occurring after V1, and history has shown that the event is over so quickly that the instruments bombs are not a threat during the takeoff roll – do not have time to respond. they are generally set to detonate at altitude. Once the air from within the engine escapes, the A surge from a turbofan engine is the result of reason (reasons) for the instability may self- instability of the engine's operating cycle. correct and the compression process may re- Compressor surge may be caused by engine establish itself. A single surge and recovery will deterioration, it may be the result of ingestion of occur quite rapidly, usually within fractions of a birds or ice, or it may be the final sound from a second. Depending on the reason for the cause “severe engine damage” type of failure. As we of the compressor instability, an engine might learned in Chapter 1, the operating cycle of the experience: turbine engine consists of intake, compression, ignition, and exhaust, which occur 1) A single self-recovering surge

2) Multiple surges prior to self-recovery The flight crew hears a very loud bang 3) Multiple surges requiring pilot action in order or double bang. The instruments will to recover 4) A non-recoverable surge. fluctuate quickly, but, unless someone was looking at the engine gage at the For complete, detailed procedures, flight crews time of the surge, the fluctuation might must follow the appropriate checklists and not be noticed. emergency procedures detailed in their specific Airplane Flight Manual. In general, however, during a single self-recovering surge, the cockpit For example: During the surge event, engine indications may fluctuate slightly and Engine Pressure Ratio (EPR) can drop briefly. The flight crew may not notice the from takeoff (T/O) to 1.05 in 0.2 fluctuation. (Some of the more recent engines seconds. EPR can then vary from 1.1 to may even have fuel-flow logic that helps the 1.05 at 0.2-second intervals two or three engine self-recover from a surge without crew intervention. The stall may go completely times. The low rotor speed (N1) can unnoticed, or it may be annunciated to the crew – drop 16% in the first 0.2 seconds, then for information only – via EICAS messages.) another 15% in the next 0.3 seconds. Alternatively, the engine may surge two or three After recovery, EPR and N1 should times before full self-recovery. When this return to pre-surge values along the happens, there is likely to be cockpit engine instrumentation shifts of sufficient magnitude normal acceleration schedule for the and duration to be noticed by the flight crew. If engine. the engine does not recover automatically from the surge, it may surge continually until the pilot Multiple surge followed by self-recovery takes action to stop the process. The desired pilot action is to retard the thrust lever until the Depending on the cause and conditions, engine recovers. The flight crew should then SLOWLY re-advance the thrust lever. the engine may surge multiple times, Occasionally, an engine may surge only once but with each bang being separated by a still not self-recover. couple of seconds. Since each bang usually represents a surge event as The actual cause for the compressor surge is described above, the flight crew may often complex and may or may not result from severe engine damage. Rarely does a single detect the "single surge" described above compressor surge CAUSE severe engine for two seconds, then the engine will damage, but sustained surging will eventually return to 98% of the pre-surge power for over-heat the turbine, as too much fuel is being a few seconds. This cycle may repeat provided for the volume of air that is reaching two or three times. During the surge and the combustor. Compressor blades may also be damaged and fail as a result of repeated violent recovery process, there will likely be surges; this will rapidly result in an engine which some rise in EGT. cannot run at any power setting. For example: EPR may fluctuate between 1.6 Additional information is provided below and 1.3, Exhaust Gas Temperature (EGT) may regarding single recoverable surge, self- rise 5 degrees C/second, N1 may fluctuate recoverable after multiple surges, surge requiring between 103% and 95%, and fuel flow may drop flight crew action, and non- recoverable surge. 2% with no change in thrust lever position. In severe cases, the noise, vibration and After 10 seconds, the engine gages should return aerodynamic forces can be very distracting. It to pre-surge values. may be difficult for the flight crew to remember that their most important task is to fly the Surge recoverable after flight crew action airplane. When surges occur as described in the last Single self-recoverable surge paragraph, but do not stop, flight crew action is required to stabilize the engine. The flight crew will notice the fluctuations described in

“recoverable after two or three bangs,” but the wide variety of flight deck symptoms as engine fluctuations and bangs will continue until the inputs are lost from electrical, pneumatic and flight crew retards the thrust lever to idle. After hydraulic systems. These situations have the flight crew retards the thrust lever to idle, the resulted in pilots troubleshooting the airplane engine parameters should decay to match thrust systems without recognizing and fixing the root lever position. After the engine reaches idle, it cause – no engine power. Some airplanes have may be re-accelerated back to power. If, upon dedicated EICAS/ECAM messages to alert the re-advancing to high power, the engine surges flight crew to an engine rolling back below idle again, the engine may be left at idle, or left at speed in flight; generally, an ENG FAIL or ENG some intermediate power, or shutdown, THRUST message. according to the checklists applicable for the airplane. If the flight crew takes no action to A flameout at take-off power is unusual – only stabilize the engine under these circumstances, about 10% of flameouts are at takeoff power. the engine will continue to surge and may Flameouts occur most frequently from experience progressive secondary damage to the intermediate or low power settings such as cruise point where it fails completely. and descent. During these flight regimes, it is likely that the autopilot is in use. The autopilot Non-recoverable surge will compensate for the asymmetrical thrust up to its limits and may then disconnect. Autopilot When a compressor surge is not disconnect must then be accompanied by recoverable, there will be a single bang prompt, appropriate control inputs from the flight crew if the airplane is to maintain a normal and the engine will decelerate to zero attitude. If no external visual references are power as if the fuel had been chopped. available, such as when flying over the ocean at This type of compressor surge can night or in IMC, the likelihood of an upset accompany a severe engine damage increases. This condition of low-power engine malfunction. It can also occur without loss with the autopilot on has caused several aircraft upsets, some of which were not any engine damage at all. recoverable. Flight control displacement may be the only obvious indication. Vigilance is EPR can drop at a rate of .34/sec and EGT rise at required to detect these stealthy engine failures a rate of 15 degrees C/sec, continuing for 8 and to maintain a safe flight attitude while the seconds (peaking) after the thrust lever is pulled situation is still recoverable. back to idle. N1 and N2 should decay at a rate consistent with shutting off the fuel, with fuel flow dropping to 25% of its pre-surge value in 2 seconds, tapering to 10% over the next 6 seconds.

Flame out

A flameout is a condition where the combustion process within the burner has stopped. A flameout will be accompanied by a drop in EGT, in engine core speed and in engine pressure ratio. Once the engine speed drops below idle, there Once the fuel supply has been restored to the may be other symptoms such as low oil pressure engine, the engine may be restarted in the warnings and electrical generators dropping off manner prescribed by the applicable Airplane line – in fact, many flameouts from low initial Flight or Operating Manual. Satisfactory engine power settings are first noticed when the restart should be confirmed by reference to all generators drop off line and may be initially primary parameters – using only N1, for mistaken for electrical problems. The flameout instance, has led to confusion during some in- may result from the engine running out of fuel, flight restarts. At some flight conditions, N1 severe inclement weather, a volcanic ash may be very similar for a windmilling engine encounter, a control system malfunction or and an engine running at flight idle. unstable engine operation (such as a compressor stall). Multiple engine flameouts may result in a

Fire disconnected or isolated from the airplane systems to prevent any fire from spreading to or contaminating associated airplane systems. This is accomplished by one common engine "fire handle." This controls the fire by greatly reducing the fuel available for combustion, by reducing the availability of pressurized air to any sump fire, by temporarily denying air to the fire through the discharge of fire extinguishant and by removing sources of re-ignition such as live electrical wiring and hot casings. It should be Engine fire almost always refers to a fire outside noted that some of these control measures may the engine but within the nacelle. A fire in the be less effective if the fire is the result of severe vicinity of the engine should be annunciated to damage – the fire may take slightly longer to be the flight crew by a fire warning in the flight extinguished in these circumstances. In the deck. It is unlikely that the flight crew will see, event of a shut down after an in-flight engine hear, or immediately smell an engine fire. fire, there should be no attempt to restart the Sometimes flight crews are advised of a fire by engine unless it is critical for continued safe communication with the control tower. flight – as the fire is likely to re-ignite once the engine is restarted. It is important to know that, given a fire in the nacelle, there is adequate time to make the first priority "fly the airplane" before attending to the fire. It has been shown that, even in incidents of Tailpipe Fires fire indication immediately after takeoff, there is adequate time to continue climb to a safe altitude One of the most alarming events for passengers, before attending to the engine. There may be flight attendants, ground personnel and even air economic damage to the nacelle, but the first traffic control (ATC) to witness is a tailpipe fire. priority of the flight crew should be to ensure the Fuel may puddle in the turbine casings and airplane continues in safe flight. exhaust during start-up or shutdown, and then ignite. This can result in a highly-visible jet of Flight crews should regard any fire warning as a flame out of the back of the engine, which may fire, even if the indication goes away when the be tens of feet long. Passengers have initiated thrust lever is retarded to idle. The indication emergency evacuations in these instances, might be the result of pneumatic leaks of hot air leading to serious injuries. into the nacelle. The fire indication could also be from a fire that is small or sheltered from the There may be no indication of an anomaly to the detector so that the fire is not apparent at low flight crew until the cabin crew or control tower power. Fire indications may also result from draws attention to the problem. They are likely faulty detection systems. Some fire detectors to describe it as an “Engine Fire,” but a tailpipe allow identification of a false indication (testing fire will NOT result in a fire warning on the the fire loops), which may avoid the need for an flight deck. IFSD. There have been times when the control tower has mistakenly reported the flames If notified of an engine fire without any associated with a compressor surge as an engine indications in the cockpit, the flight crew should "fire." accomplish the tailpipe fire procedure. It will include motoring the engine to help extinguish In the event of a fire warning annunciation, the the flames, while most other engine abnormal flight crew must refer to the checklists and procedures will not. procedures specific to the airplane being flown. In general, once the decision is made that a fire Since the fire is burning within the turbine casing exists and the aircraft is stabilized, engine and exhaust nozzle, pulling the fire handle to shutdown should be immediately accomplished discharge extinguishant to the space between by shutting off fuel to the engine, both at the casings and cowls will be ineffective. Pulling engine fuel control shutoff and the wing/pylon the fire handle may also make it impossible to spar valve. All bleed air, electrical, and dry motor the engine, which is the quickest way hydraulics from the affected engine will be of extinguishing most tailpipe fires.

Hot starts

During engine start, the compressor is very inefficient, as already discussed. If the engine experiences more than the usual difficulty accelerating (due to such problems as early starter cut-out, fuel mis-scheduling, or strong tailwinds), the engine may spend a considerable time at very low RPM (sub-idle). Normal engine cooling flows will not be effective during sub- idle operation, and turbine temperatures may Fig 13 showing fan blades bent by encounter appear relatively high. This is known as a hot with a bird. start (or, if the engine completely stops accelerating toward idle, a hung start). The Bird ingestion can also result in an engine surge. AFM indicates acceptable time/temperature The surge may have any of the characteristics limits for EGT during a hot start. More recent, listed in the surge section. The engine may surge FADEC-controlled engines may incorporate once and recover; it may surge continuously auto-start logic to detect and manage a hot start. until the flight crew takes action; or it may surge once and not recover, resulting in the loss of Bird ingestion/FOD power from that engine. Bird ingestion can result in the fracture of one or more fan blades, Airplane engines ingest birds most often in the in which case, the engine will likely surge once vicinity of airports, either during takeoff or and not recover. during landing. Encounters with birds occur during both daytime and nighttime flights. Regardless of the fact that a bird ingestion has By far, most bird encounters do not affect the resulted in an engine surge, the first priority task safe outcome of a flight. In more than half of the of the flight crew is to "fly the airplane." Once bird ingestions into engines, the flight crew is the airplane is in stable flight at a safe altitude, not even aware that the ingestion took place. the appropriate procedures in the applicable Airplane Flight Manual can be accomplished. When an ingestion involves a larger bird, the flight crew may notice a thud, bang or vibration. In rare cases, multiple engines can ingest If the bird enters the engine core, there may be a medium or large birds. In the event of suspected smell of burnt flesh in the flight deck or multiple-engine damage, taking action to passenger cabin from the bleed air. stabilize the engines becomes a much higher priority than if only one engine is involved – but Bird strikes can damage an engine. The photo it is still essential to control the airplane first. below shows fan blades bent due to the ingestion of a bird. The engine continued to produce thrust with this level of damage. Foreign Object Damage (FOD) from other sources, such as tire fragments, runway debris or animals, may also be encountered, with similar results. Severe engine damage

engine– the fan has too much inertia, and the rotor is being pushed around by ram air too forcefully to be stopped by the static structure. The HP rotor is more likely to seize after an in- flight shutdown if the nature of the engine malfunction is mechanical damage within the HP system. Should the LP rotor seize, there will be some perceptible drag for which the flight crew must compensate; however, if the HP rotor seizes there will be negligible effect upon airplane handling

Seizure cannot occur without being caused by Severe engine damage may be difficult to define. very severe engine damage, to the point where From the viewpoint of the flight crew, severe the vanes and blades of the compressor and engine damage is mechanical damage to the turbine are mostly destroyed. This is not an engine that looks "bad and ugly." To the instantaneous process – there is a great deal of manufacturers of the engine and the airplane, inertia in the turning rotor, compared to the severe engine damage may involve symptoms as energy needed to break interlocking rotating and obvious as large holes in the engine cases and static components. nacelle or as subtle as the non-response of the engine to thrust lever movement. Once the airplane has landed, and the rotor is no longer being driven by ram air, seizure is It is important for flight crews to know that frequently observed after severe damage. severe engine damage may be accompanied by symptoms such as fire warning (from leaked hot Symptoms of engine seizure in flight may air) or engine surge because the compressor include vibration, zero rotor speed, mild airplane stages that hold back the pressure may not be yaw, and possibly unusual noises in the event of intact or in working order due to the engine fan seizure. There may be an increased fuel flow damage. in the remaining engines due to aircraft automatic compensations; no special action is In this case, the symptoms of severe engine needed other than that which is appropriate to the damage will be the same as a surge without severe engine damage type failure. recovery. There will be a loud noise. EPR will drop quickly; N1, N2 and fuel flow will drop. EGT may rise momentarily. There will be a loss of power to the airplane as a result of the severe Engine Separation engine damage. It is not important to initially distinguish between a non-recoverable surge Engine separation is an extremely rare event. It with or without severe engine damage, or will be accompanied by loss of all primary and between a fire and a fire warning with severe secondary parameters for the affected engine, engine damage. The priority of the flight crew noises, and airplane yaw (especially at high still remains "fly the airplane." Once the power settings). Separation is most likely to airplane is stabilized, the flight crew can occur during take-off/climb-out or the landing diagnose the situation. roll. Airplane handling may be affected. It is important to use the fire handle to close the spar valve and prevent a massive overboard fuel leak; refer to the Airplane Flight or Operations Manual Engine Seizure for specific procedures.

Engine seizure describes a situation where the engine rotors stop turning in flight, perhaps very Fuel System Problems suddenly. The static and rotating parts lock up against each other, bringing the rotor to a halt. In practice, this is only likely to occur at low Leaks rotor RPM after an engine shutdown, and virtually never occurs for the fan of a large

Major leaks in the fuel system are a concern to system, the engine fuel control may no longer the flight crew because they may result in engine operate as intended. There is a potential for fire, or, eventually, in fuel exhaustion. A very multiple-engine flameout. The Airplane Flight large leak can produce engine flameout. or Operating Manual provides the necessary guidance. Engine instruments will only indicate a leak if it is downstream of the fuel flowmeter. A leak between the tanks and the fuel flowmeter can Oil System Problems only be recognized by comparing fuel usage between engines, or by comparing actual usage to planned usage, or by visual inspection for fuel The engine oil system has a relatively large flowing out of the pylon or cowlings. number of indicated parameters required by the Eventually, the leak may result in tank regulations (pressure, temperature, quantity, imbalance. filter clogging). Many of the sensors used are subject to giving false indications, especially on In the event of a major leak, the crew should earlier engine models. Multiple abnormal consider whether the leak needs to be isolated to system indications confirm a genuine failure; a prevent fuel exhaustion. single abnormal indication may or may not be a valid indication of failure. It should be noted that the likelihood of fire resulting from such a leak is greater at low There is considerable variation between failure altitude and when the airplane is stationary; even progressions in the oil system, so the symptoms if no fire is observed in flight, it is advisable for given below may vary from case to case. emergency services to be available upon landing. Oil system problems may appear at any flight phase, and generally progress gradually. They Inability to shutdown Engine may lead eventually to severe engine damage if the engine is not shut down.

If the engine fuel shut-off valve malfunctions, it may not be possible to shut the engine down by Leaks the normal procedure, since the engine continues to run after the fuel switch is moved to the cutoff position. Closing the spar valve by pulling the Leaks will produce a sustained reduction in oil fire handle will ensure that the engine shuts quantity, down to zero (though there will still be down as soon as it has used the fuel in the line some usable oil in the system at this point). from the spar valve to the fuel pump inlet. This Once the oil is completely exhausted, oil may take a couple of minutes. pressure will drop to zero, followed by the low oil pressure light. There have been cases where maintenance error caused leaks on multiple Fuel filter Clogging engines; it is therefore advisable to monitor oil quantity carefully on the good engines as well. Rapid change in the oil quantity after thrust lever Fuel filter clogging can result from the failure of movement may not indicate a leak – it may be one of the fuel tank boost pumps (the pump due to oil “gulping” or “hiding” as more oil generates debris which is swept downstream to flows into the sumps. the fuel filter), from severe contamination of the fuel tanks during maintenance (scraps of rag, sealant, etc., that are swept downstream to the Bearing failures fuel filter), or, more seriously, from gross contamination of the fuel. Fuel filter clogging will usually be seen at high power settings, when Bearing failures will be accompanied by an the fuel flow through the filter (and the sensed increase in oil temperature and indicated pressure drop across the filter) is greatest. If vibration. Audible noises and filter clog multiple fuel filter bypass indications are seen, messages may follow; if the failure progresses to the fuel may be heavily contaminated with water, severe engine damage, it may be accompanied rust, algae, etc. Once the filters bypass and the by low oil quantity and pressure indications. contaminant goes straight into the engine fuel

Oil pump failures • Significant differences between primary parameters from one engine to the next. Oil pump failure will be accompanied by low indicated oil pressure and a low oil pressure If asymmetric thrust is suspected, the first light, or by an oil filter clog message. response must be to make the appropriate trim or rudder input. Disconnecting the autopilot without first performing the appropriate control input or trim may result in a rapid roll maneuver. Contamination

Contamination of the oil system – by carbon Reverser malfunctions deposits, cotton waste, improper fluids, etc. – will generally lead to an oil filter clog indication or an impending bypass indication. This Generally, thrust reverser malfunctions are indication may disappear if thrust is reduced, limited to failure conditions where the reverser since the oil flow and pressure drop across the system fails to deploy when commanded and filter will also drop. fails to stow when commanded. Failure to deploy or to stow during the landing roll will result in significant asymmetric thrust, and may require a rapid response to maintain directional No Thrust Lever Response control of the airplane. Uncommanded deployments of modern thrust reverser systems A “no Thrust Lever Response” type of have occurred and have led to Airworthiness malfunction is more subtle than the other Directives to add additional locking systems to malfunctions previously discussed, so subtle that the reverser. As a consequence of this action, the it can be completely overlooked, with potentially probability of inadvertent deployment is serious consequences to the airplane. extremely low. The Airplane Flight or Operations Manual provides the necessary If an engine slowly loses power – or if, when the system information and type of annunciations thrust lever is moved, the engine does not provided by the airplane type. respond – the airplane will experience asymmetric thrust. This may be partly concealed by the autopilot’s efforts to maintain the required No Starter Cutout flight condition.

If no external visual references are available, Generally, this condition exists when the start such as when flying over the ocean at night or in selector remains in the start position or the IMC, asymmetric thrust may persist for some engine start valve is open when commanded time without the flight crew recognizing or closed. Since the starter is intended only to correcting it. In several cases, this has led to operate at low speeds for a few minutes at a time, airplane upset, which was not always the starter may fail completely (burst) and cause recoverable. Vigilance is required to detect these further engine damage if the starter does not cut stealthy engine failures and to maintain a safe out. flight attitude while the situation is still recoverable. As stated, this condition is subtle and not easy to detect. Vibration

Symptoms may include: Vibration is a symptom of a wide variety of • Multiple system problems such as engine conditions, ranging from very benign to generators dropping off-line or low engine serious. The following are some causes of tactile oil pressure or indicated vibration: • Unexplained airplane attitude changes • Fan unbalance at assembly • Large unexplained flight control surface • Fan blade friction or shingling deflections (autopilot on) or the need for • Water accumulation in the fan rotor large flight control inputs without apparent

cause (autopilot off) • Blade icing • Bird ingestion/FOD

• Bearing failure parameters will help to establish whether a • Blade distortion or failure failure exists. • Excessive fan rotor system tip clearances. Vibration felt on the flight deck may not be It is not easy to identify the cause of the indicated on instruments. For some engine vibration in the absence of other unusual failures, severe vibration may be experienced on indications. Although the vibration from some the flight deck either during an engine failure failures may feel very severe on the flight deck, and possibly after the engine has been shut it will not damage the airplane. There is no need down, to the point where instruments are to take action based on vibration indication difficult to read. This large amplitude vibration alone, but it can be very valuable in confirming a is caused by the unbalanced fan windmilling problem identified by other means. close to the airframe natural frequency, which may amplify the vibration. Changing airspeed Engine vibration may be caused by fan and/or altitude will change the fan windmill unbalance (ice buildup, fan blade material loss speed, and an airplane speed may be found due to ingested material, or fan blade distortion where there will be much less vibration. due to foreign object damage) or by an internal Meanwhile, there is no risk of airplane structural engine failure. Reference to other engine failure due to vibratory engine loads.

Wrap-up

The tabulation of engine conditions and their symptoms below shows that many failures have similar symptoms and that it may not be practicable to diagnose the nature of the engine problem from flight deck instrumentation. However, it is not necessary to understand exactly what is wrong with the engine – selecting the “wrong” checklist may cause some further economic damage to the engine, but, provided action is taken with the correct engine, and airplane control is kept as the first priority, the airplane will still be safe.

y lo p Engine separation Severe damage Surge Bird ingestion/FOD Seizure Flameout Fuel control problems Fire fires Tailpipe Hot start Icing Reverser inadvertent de Fuel leak

Bang O X X O O O

Fire Warning O O O X

Visible flame O O O O O X O

Vibration X O X O X X

Yaw O O O O O O O X

High EGT X X O O X O X O

N1 change X O O O X X X X

N2 change X O O O X X X X

Fuel flow change X O O O X O O X

Oil indication X O O O? X O change

Visible cowl X X O X damage

Smoke/odor in O O O cabin bleed air

EPR change X X X O X X X X

X = Symptom very likely O = Symptom possible Note: blank fields mean that the symptom is unlikely

Appendix

Attached are flash card style summary descriptions of many of the malfunctions discussed in this text.

Engine Stall/Surge

Event Description Symptoms Engine Stall or Surge is a momentary reversal of the High power: Loud bang and yaw (may compressor airflow so that high-pressure air escapes be repetitive). out of the engine inlet. Flames from inlet and tailpipe. Vibration. High EGT/TGT. Corrective action Parameter fluctuation

After stabilizing airplane flight path, observe engine Low power: Quiet instruments for anomalies. Stall/surge may be self- bang/pop or rumble. correcting, may require the engine to be throttled back, or may require engine shutdown, if the engine can be positively identified and the stall will not clear.

POSSIBLE MESSAGES EPR

ENG STALL

EGT OVERLIMIT

EGT ENG FAIL

FLUX N2

Flameout

Event Description Symptoms Engine Flameout is a condition where the combustor is Single engine: Core speed, EGT, EPR all no longer burning fuel. decay. Electrical generator drops off line; low oil pressure Corrective action warning as core speed drops below After stabilizing airplane flight path, verify fuel supply to idle. engine. Re-start engine according to AFM. Multiple engines: As above, but also hydraulic, pneumatic and electrical system problems.

POSSIBLE MESSAGES EPR

ENG FAIL

OIL LO PR

EGT GEN OFF

BLD OFF

N1 ALL ENG FLAMEOUT

LOW N2

Fire

Event Description Symptoms Engine fire is a fuel, oil or hydraulic fluid fire between Fire warning. Flame or smoke may be the engine casing and the cowlings (or occasionally a observed. metal fire). It could result from severe damage. Hot air leaks can also give a fire warning.

Corrective action After stabilizing airplane flight path, shut the engine down and discharge extinguishant. Avoid restarting the engine.

POSSIBLE MESSAGES EPR

ENG FIRE

EGT

NORMAL N2

PARAMETERS MAY LOOK NORMAL

Tailpipe fire

Event Description Symptoms Fuel puddles in the tailpipe and ignites on hot surfaces. Observed flames and smoke. No fire warning. Corrective action Shut off fuel to the engine and dry motor it.

POSSIBLE MESSAGES EPR

START FAULT

EGT

LOW N2

Bird Ingestion

Event Description Symptoms A bird (or other creature) is sucked into the engine inlet. Thud, bang, vibration. Odor in cabin. Surge Note; ingestion of ice slabs, blown tires, etc., will may result from bird produce similar, more severe symptoms. ingestion.

Corrective action After stabilizing airplane flight path, watch engine instruments for anomalies. If the engine surges, throttle back or shut down as necessary. If multiple engines are affected, operate engines free of surge/stall to maintain desired flight profile.

POSSIBLE MESSAGES EPR

ENG STALL

EGT OVERLIMIT

EGT VIB

NORMAL N2

PARAMETERS MAY LOOK NORMAL 59

Severe Engine Damage

Event Description Symptoms The engine hardware is damaged to the point where the Depending on nature of damage – engine is in no condition to run – such as bearing surge/stall, vibration, failure, major fan damage from ingestion of foreign fire warning, high EGT, oil system objects, blade or rotor disk failures, etc. parameters out of limits, rotor speed Corrective action and EPR decay, yaw. After stabilizing airplane flight path, observe engine instruments for anomalies. Shut down engine.

POSSIBLE MESSAGES EPR

ENG FAIL

EGT OVERLIMIT

EGT ENG STALL

VIB

OIL LO PR N1

LOW N2

Engine Seizure

Event Description Symptoms Engine seizure is the locking up of one or more rotors. After shut down, zero speed on one of the It only happens after engines are shut down for severe rotors. Minor damage. increase in required thrust for flight Corrective action conditions. Trim and adjust power for increased drag.

POSSIBLE MESSAGES EPR

ENG SHUT DOWN

EGT

LOW N2

Engine Separation

Event Description Symptoms Engine Separation is the departure of the engine from Loss of all engine parameters. the airplane due to mount or pylon failure. Hydraulic, pneumatic and electrical system Corrective action problems After stabilizing airplane flight path, observe engine instruments for anomalies. Turn off fuel to appropriate engine.

POSSIBLE MESSAGES EPR

ENG FIRE

HYD OFF

EGT GEN OFF

BLD OFF

ZERO N2